After a tough / level match one loses a lot of energy and needs time to recover. But after a win he feels high and can play on.

what i find in blitz/quick games is that the errors one makes become predictable so it is not an anonymous game anymore.  Instead it becomes trying to cause the opponent to make similar errors.  For that reason i tend to decline all rematches of games less than 10 mins.  Just my opinion.

everybody has a free choice in leaving or accepting, it's as simple as that. 

One can speculate all one wants.  Sometimes I've just got time for one quick game, and whether I win or lose I can't stay to play another.  A person's motivation for declining a rematch can vary greatly and can have very little to do with the game you just played.