How to get better at OTB chess?

I am looking for suggestions on how to get better at standard tournament chess. I think I am reasonably ok at blitz chess(though I may be seriously mistaken about that too) since I have a rating of around 1700 here and on Playchess.

The damndest thing is that I can just not play tournament chess. If I create a single weaknes, then that is ruthlessly exploited as is possible when you have a long time to think. I will many times make a move and then instantly regret it. My FIDE rating is about 1280. I am presently in a tournament and before the tournament game I asked a 1490 to play a few blitz games and I crushed him in both games as Black. However, when I am in an actual tournament game and when the clocks start my mind goes blank and I find myself ruminating on totally weird bizarre and unrealistic things. What if my opponent plays this plays that, if I do this he will do that if I do that he will do that. In fact with only two pieces out in the opening I am already thinking of a 'plan'. I have seen that the more seasoned players just develop normally and then take it from there. But for me I just get beaten right in the opening. I have been beaten by some really bad players only because I played even worse.

How do I build up the tenacity and mind set to be able to play tournament chess?

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Well Na6 is just a bad move. You are not Magnus Carlsen. Follow Toatsev's Principles and don't try be a putz with your knight.

EDIT: I have this same problem by the way. Don't kid yourself, its a huge matter of experience. I find that by taking my time and making sure that I am sure of my moves I do much better. That's actually the hardest part of chess.

Actually Na6 might have been a bad move but the real mistake was f5 I think.

To the first point, the more time I spend the worse my confusion becomes. I am so used to 5 min chess that my thinking process is optimized and I am able to use my time well. In real chess I make these terrible moves with no double checking. 

Yes, I think experience is very important. The more you play standard OTB games, the better, but meanwhile you could play at least 30/0 or 45/45 online games here when you have the chance. Also analyzing those type of games is a great help.

Work on sensible development and take your time. Don't rush your moves. Here 7...Be7 is a wasted move. You then follow that up with 8...f5 which is weakening. Then you play 9...c6 why? You'd got a horrible position from move 9. Just develop your pieces.

I have a feeling that there's more going on than this single game shows. 

In serious OTB chess, it's easy to see ghosts and second guess yourself. It's not just about taking your time, it's about having a good method of deciding what moves to consider and make. One of the most important things you can learn is to trust your own analysis. This takes targetted practice. 

Try setting up complex positions which occur in real games (preferrably ones that have excellent annotations) before anything is decided. Spend at least 20 minutes coming up with a plan. Work out all the tactics you can, then write everything down. When you're done, compare that with the notes to the game. Do not make a move until the 20 minutes are up, even if you think you've "solved" the position. Keep analysing more deeply.

Do that at least once a week (once a day or more if you're wanting to improve quickly), and you will see your decision making improve dramatically.  

Stop playing blitz, and play some slow chess here on chess.com. It's probably just about you getting used to take your time and examine the position thoroughly before making a move.

I disagree with that advice. Keep playing blitz. It helps with pattern recognition and other important aspects of the game. But definitely make time to play slower time controls, and to do those 20 minute exercises (which actually take about 30 minutes or more).

I aldo think that playing longer games on the Internet from time to time and analyzing them should help. Your good blitz rating shows you have some natural aptitude for the game.

You may be right.

I think the need to focus more on longer games is clear though.

Play longer time controls a lot and get used to it. Give up the blitz for a while and play just longer times.... eventually you'll get used to it.....

SLOW DOWN! spend 3 minutes per move.

same problem here

8. ... f5 looked like a real lemon. Nearly all of your subsequent problems can be traced to that weakening move... the weak e6-Pawn that forced you to develop the Knight on a6 instead of its natural square at d7, the weakness on the c4-g8 diagonal, the hanging Bishop on d7... all were consequences of 8. ... f5.

My advice for avoiding OTB blunders: sit on your hands. It worked for me. The small act of lifting yourself slightly to take your hands out to make a move acts as a reminder to blunder-check before moving.