Throwing in a little bit of psychology in chess :-)
I've written about, and shown before, several games in which the opponent starts blundering right after an unexpected queen sac.
Another thing that I have noticed is the following :
- Get a lost or seemingly lost position
- Start thinking for a really long time
- Don't resign but continue playing
- Increase the speed of making the moves after the long thinking
- .....
- Profit !!! :-)
Here's a game in which that just happened. I was a bit absent minded, and my opponent played a bit of an unusual gambit in which there was very little compensation.
Then I blundered a pawn, and suddenly I disliked my position, and even thought about resigning.
Then I thought for a long time, and continued.
Very soon the opponent blundered and resigned.
I believe that by long thinking in a worse position, especially in slow time control over the board chess games, can give the opponent more time to get into the "Hey-I-have-a-won-position" feeling, which sometimes can cause a temporarily lack of alertness and concentration.
For further reading :
http://www.wikihow.com/Use-Psychology-to-Win-Chess-Games
http://en.chessbase.com/post/psychology-the-heart-of-che
https://archive.org/stream/jstor-1412592/1412592#page/n1/mode/2up
http://lifehacker.com/2-psychology-rules-for-getting-better-at-chess-and-lif-1471934170