long practice in chess reduces time of thinking. by the way I play chess in the evening after a hard day of studying and working, so I'm very very slow...
I can't tell you how many times I rushed a move (cuz i thought it was perfect) only to see after I'd moved that i was a stupid move. The longer you take, the more chance you have of catching mistakes before you've made them.
why is that most players dont play faster than they do?