Was this lack of opening knowledge, or general inexperience?

Pawn position can also be development so why not an early a3 to prepare for b4?

Opening was fine, middlegame was not.

c5 is a good pawn break if you get to play all the moves you'd been planning on, but black gets to move too, so your idea was just very slow. So, I should focus mainly on the plans already possible in the position, as opposed to just blindly following the first one I come across?

What can black do? Exactly what he did in the game. 12...a5 threatens to open lines. How to tell who that will favor? Almost always whoever is better developed. Black's rooks are connected and white's are not, so it will probably favor black. Also white has claimed a lot of space, but only has 2 minor pieces, so already white's position is feeling shaky. So you needed to play 13.b5 to keep things closed. I hadn't assessed it this way, unfortunately... All I saw was the space. Even more embarassing since I have recently worked through Jeremy Silman's "How to Reassess Your Chess", which specifically focusses on imbalances.

16.d5 is a fine move, but lets use that position to assess. White has the worse pawn structure (two pawn islands to black's 1). White's a pawn is an isolated pawn on a half open file, so it's vulnerable to attack. Black has the c5 square for his knight. So this is the conversation of the game for a while.

Then you play 24.f4

First of all, all your pieces are on the queenside, so this pawn break looks a little funny.

More importantly, whose pawn mass do you think is more vulnerable? Black's b6-c7-d6 or white's d5-e4? White's pawns look worse. After move 25 we can see e4 is a backward pawn on an open file. c7 is too, but black has extreme control over c5, and can block that file with a piece any time. So now black has two targets (a2 and e4) while white really has none. I know you say this move was desperation, but it is not a good desperation move to give your opponent more ways to attack you 

If you had mutual attacking chances, ok, fine, but black is the only one happy with f4 (if you had started by moving a lot of pieces to the kingside first that might be a different story). I thought it was okay to play f4, simply because I didn't see any other ways to give him issues to think about, and if I do nothing, my knight on c6 will be traded away, and my a pawn will probably be captured... All this convinced me that I was already pretty dead here.

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So that's what hurt you this game, strategic understanding. You hurt your own pawn structure (allowing black to capture on b4 and playing f4) and black had weak pawns to target while you didn't. I am always trying to capture that elusive skill "strategy", and especially where pawn structure is concerned, I am often eluded.

Experience wise, I suppose your c5 plan was inexperience. It's fine if you get to make the 4 or 5 moves you wanted, but it's a very slow moving plan and that hurt you. So, play the position, as Jeremy Silman would say, not whatever you want to play. 

Thanks for all your feedback, back to the strategy books I go!

Cheers,

William

 So, I should focus mainly on the plans already possible in the position, as opposed to just blindly following the first one I come across?

I hadn't assessed it this way, unfortunately... All I saw was the space. Even more embarassing since I have recently worked through Jeremy Silman's "How to Reassess Your Chess", which specifically focusses on imbalances. 

  I thought it was okay to play f4, simply because I didn't see any other ways to give him issues to think about, and if I do nothing, my knight on c6 will be traded away, and my a pawn will probably be captured... All this convinced me that I was already pretty dead here.

  I am always trying to capture that elusive skill "strategy", and especially where pawn structure is concerned, I am often eluded.

 So, play the position, as Jeremy Silman would say, not whatever you want to play. 

It's hard to give general advice because there are always so many exceptions. You did well to spot a pawn break and go for it, so that's actually something to feel good about. It's just in this position it didn't work out. It's not a "oh my gosh c5 is so dumb" mistake, more like a live and learn mistake.

 Space is tricky, I'm still trying to understand it correctly. The tricky thing for me is pawns are most safe on the 2nd rank. Every time they move closer to the enemy side, they get a little more vulnerable to attack (generally speaking). But they also gain space for your pieces. Also what's good in the mid game might be weak in the endgame.

So it's often hard to judge a pawn moves, so don't feel too bad

A quote from Carlsen about defending a worse position:

When you are behind there are two strategies – counter-attack or all men to the defenses. I’m good at finding the right balance between those.

So again, this is another difficult decision in chess.

f4 as part of a counter attack is fine, but maybe prep it first with moves like Ne7 then Nf5, now after f4 he can't capture right away because Qxg7 is mate for example. You have time to prep because it will still take a long time to pile up on a2 / organize his pieces.

I really liked Soltis' book "Pawn Structure Chess."

However, having a certain level of habitual blunder checking / tactical checking helps make strategy more clear, because when you and your opponents aren't losing to blunder as often, the smaller things start to be more noticable.

When you're new to an opening it's good to just get some ideas by looking at GM games. Just 5 to 10 minutes a game, and you're not trying to understand every move. Note things like:

 - What side of the board (queenside, center, or kingside) does each player usually seek play on?
 - How do they seek play? Pawns or pieces?
 - What pawn breaks do the players normally go for?

You can google, for example "queen's indian defense chessgames.com" and you'll get this page:

http://www.chessgames.com/perl/chessopening?eco=e12

I think you played pretty well. You did pitch a pawn, but you had some compensation, and you were only a little worse.  But you kind of freaked out when he played 23...Nd7. It's true that your knight was pretty well posted on c6, but it wasn't the world's greatest outpost, and moving it wasn't going to kill you. Suppose you play 24.a4 with the idea of a5 and breaking up the black king side? If 24...Ndb8 you have 25.Ne7+ Kh8 26.Nf5. You are going to play Rfb1 and a5 and liquidate the queen side. I think you could draw

A few thoughts on the game.I haven't read what others said so I might say the same things.

   First you talk about Catalan.If you wanted to play Catalan you should play 3.g3.After 3.Nf3 it's not Catalan unless Black allows it I think White generally has essentially the same idea in the 4. g3 variation of the QID as he does in the Catalan... Plus 3. Nf3 reveals my intentions less than 3. g3 does. I will try both ways,  and see what works for me. Thanks for pointing that out!

You panik without reason.After he took the pawn you were fine.

      You are a good player , much better than your rating here but yo don't let yourself pay good chess because you play with your emotions. I was just thinking about this the other day; I tend to play much better when I am relaxed and happy, rather than when I try to ride myself like a taskmaster and get frustrated at mistakes.

Here are some of your comments:

13th move

"It was at this moment that I saw myself beginning to teeter. Maybe d5 here immediately? Instead I was spooked by the tension, and decided on"

16th move

"but the isolated a-pawn is really coming to bite me on the rear..."

17th move

"I have been crushed in the English this way before."

"An absolute terror of a knight."

24th move

"Desperation".

     As I already showed you , on 24th move , when you are desperate , your position is actually fine.

If you could calm for a minute and do a cold blooded evaluation you woud see that there is nothing to be afraid of. I was wondering if there was... You're right. If I could look at things based on my chess knowlege, as opposed to what I "feel", I would be a much better player. Now, to put it into practice!

    My guess is that you were playing against a player that you consider better than you.You lost that game before you started.On move 4 you already say that you are out of your prep like you are playing aginst a GM or something and on move 7 you are wondering if there is something wrong with your move that is perfectly normal. In fact, he was much "better", so to speak; much more experienced, and, of course, much higher rated. My question on the 7th move was asking about theory though, as all players in my database recapture with the Queen.

    Every time you feel that you panik , take a deep breath , close your eyes for a few seconds , then opened them and try to do a cold-blooded evaluation of the position.If you still decide that your position is bad , you must still try to find the way to make your opponent's life as difficult as possible.Your opponent is under psychological pressure when he is better.He feels that he must win.Most of the mistakes happen on this stage.But to take advantage of them you must create some kind of pressure. So, my issue is basically emotional evaluation. 

          Chess needs confidence more than opening prep or anything else and you don't have any.You must not let your emotions and your fears decide  your moves.If you can't do that , you can't play chess.

Losing in the middlegame because of tactics has nothing to do with lack of opening knowledge or experience.