Had my opponent on the verge of a checkmate - and broke down completely - Why ?

This is a game I just played. Had my opponent on the verge of a checkmate most of the time. I could not make the final blow. I was so exhausted of thinking and calculating and not making a checkmate that I suddenly became weak and gave up. In adition I was again very stressed after not succeeding (see my topic in the general section).

Do you see what went wrong for me ? What couldn`t I win this ?

I will not comment on specific moves except for my suggestion with 24. Rxc6 instead of Qxc6. You had a stronger position obviously, but you let him keep all his pieces and then dilly-daddled around the board until he found an opening.

When you had such an advantage, you need to bring your attack and get his pieces off the board. This is just a process of learning the game! I had so many times where I wanted a checkmate earlier than the board would allow. You have to be patient and make sure you are making good moves. In this case, these cautious moves were not very strong.

Feeding this into the computer analysis engine I have:

After you did 14. Na7 Kb8 15. Nc6+ bxc6 16. a4, the computer engine says you have no mate and you are basically down a knight.

20...Kc7 was a mistake, which is losing, but there is no mate. 20...Ka7 would have kept black's advantage. Instead of 22. Rc1, you should have played 22. Qb7+.

There is actually no immediate mate, so you should just have gone for  with 27. Bxc7 where, after a few moves, you end up with a passed a-pawn and an exchange up.

Either one of 24. Qxc6 or 24. Rxc6 work well enough.

Black's 27...f5 gives you back the advantage, you should have played 28. Qb7. 29. Rb7 was your last chance to keep White's advantage, where you keep your attack going.

While Black's king was partially the reason why you had an advantage on the queenside, the main reason for your advantage was the activity of your pieces on the queenside. Chasing the king with your queen on the kingside kind of meant you weren't using white's strengths on the queenside.

I went over this game, and to tell you the truth, it's very complicated and has lots of tactics. So I think this is a bad example to choose for beating yourself up.

One mistake that was obvious was allowing your knight to get trapped with 14.Na7+. If you had looked at your opponent's possible response threat of 14...Kb8, you might have realized that your knight was trapped. (This is a good example of playing hope chess instead of real chess.)

Will read your suggestions from my other topic - especially Silman on `hoe chess`. Thanx for hints.

Also, you missed some easier wins. 12.d5 wins a bishop (or a knight) for a pawn.

A strong player once told me that when I'm attacking, the opposing player can almost always give up some material to stop the attack and avoid mate. If you're too focused on finding checkmate, you'll miss the opportunity to take some material that you can later convert to a win, and if there is no mate, then you'll use up your positional advantage and get nothing out of it. In short, take what advantage you can get, and don't push too hard for one that you can't. This is one reason why knowing your endgames is very handy--you can be confident that you can win if you take the extra material and go to an advantageous endgame. If your endgames aren't very good, then you're more likely to push for the mate now as opposed to taking what would otherwise be the "sure" win later.

King hunts are always hard, just because you have to calculate every possible response, even if it's a piece sacrifice, because your pieces tend to get very uncoordinated. 

As for getting exhausted by the end of the game--that happens a lot too. You're frantically calculating everything you can see, non-stop, for an hour.

@ Lucidish_Lux:

Wisely and helpful spoken as always from you. Thanx again. After the battle smoke`s gone I learnt that sacrificing of material could have been a way. I am still too afraid of giving material for gaining advabtages. I admit that I have to study more into this calculation thing.

@ BorgQueen:

Absolutely helpful. Thanx.