Need help!!!

My chess is going to custard. I seem to be winning and then I get destroyed by an unseen trap. Can I please have some analysis of this example

Sorry to say, but after 21.  Nf6???? you were dead.  You would have had the game with almost any other move.

Okay thanks for the help

You have received some help from a NM and I would not presume to improve on that but thought maybe some general impressions might be helpful. Perhaps NMtonydal would either agree or correct my "feeling" based on a very quick runthrough of the game. At the end, your fighting pieces are clumped together ineffectively positioned on the Q-side. In the early going there seemed to be a lot of pawn movement and other moves which did not have a clear purpose. It just seemed that your concentration may not have been at it's best on every move. We are all guilty of that and we all lose games because of it. Again, not a technical analysis, just an impression. Good luck.

That was a pretty good game.  Nf6 killed you, but was unnoticeable.

I think there's a lot to learn from 21...Nf6??  I read TonyDal's comments before going thru your game, so I just clicked to move 21 and looked at Nf6. I expected Nf6 to jump out at me as a blunder, but instead it looked, at first glance, like a reasonable move.  So the challenge is -- what makes Nf6 so bad and what do we need to see in order to avoid it. A very strong tactician might "see" the lines that follow from Nf6 and how disadvantageous they are for black -- but we can't just wish ourselves to be stronger calculators with quicker minds.  I think here what we can do is have a clear strategic understanding of the position, and use that to guide our choice of moves. 

Some positions are hard (impossible! at least for me) to understand strategically... but others are rather clear. I think if you assess your position at move 21 it's pretty easy to say what the situation is: You have a significant material advantage... but your King is endangered. White has a rook holding a lovely open file for attack, and white looks poised to bring his pieces into attack on your Kingside in just a few moves... meanwhile the majority of your pieces are positioned very awkwardly for defense over on the queenside. Only your N's are holding the line against the enemy horde.

This isn't a subtle or deep understanding of the position. It's quite basic. But all the same it should give us some ideas about what to do, and what NOT to do.

what to do?

Well... you want to bring your pieces into the defense (and into position for counterattack of course if at all possible), you want to exchange away his attackers (exchanges benefit you in the long term since you already have a material advantage and they benefit in the short term because they should help defuse his attack) and you want to clog his attack. Prevent him from opening lines and penetrating further into your postion. Two final considerations: you might want to think about getting the King the hell out of there... (if the defenders can't get to him, maybe he can get to the defenders?) and since you are up a piece, you should remember you always have the option of sac'ing back a piece, if things get desperate, to get your King out of hot water. 

Looked at this way... you should see that you want to keep his Queen and his Bishop from getting involved in this fight. You want to keep him as clogged up as possible while finding moves that free your pieces.  You should be able to see that your e-pawn is crucial in both regards. Nf6 is terrible because it means after Nxf4 the exf4 recapture opens the floodgates for the white pieces. It opens up the diagonal for his bishop, and the natural Q x P recapture improves his Queen's position.

Wouldn't looking at the position this way help you find a more suitable move and help you see what's wrong with Nf6? Strategic thinking does not substitute for tactical sight but it does augment and sharpen it IMO.

You want to activate your pieces for defense...  Your N was already involved in the defense... get some help! My first thought is f4 -- but Tonydal mentioned several other candidates.