In another thread Greenspawn comments that one magazine showed how rather then why games were lost.
I am attempting to list of the reasons why you could lose a game, so here goes:
1. Lack of knowledge of the rules (e.g. en passant)
2. Lack of technical knowledge (e.g. coming out worse from an opening, not understanding oppositions in an ending),
3. Outright blunder (e.g. leaving a piece to be taken)
4. Missing tactics by opponent
5. Failing to find the correct continuation in a tactical exchange yourself
6. commencing a losing tactic against your opponent
7. Lacking a plan in the middle/end game
8. Having a worse plan than your opponent in the middle/endgame
9. Having a good plan but failing to properly execute it
10. Lack of time (i include skulls in this category)
11.Moving too quickly
12. PLaying whilst "tired and emotional"
The list is clearly not exhaustive and please add and in truth normally a combination. The answer may be educational if repeated often enough. You can then diagnose the appropriate remedy Mine was 3 and 12 but more commonly in my matches 7/8.