Spotting ones mistakes!

Hello,

Another n00b post from the man himself (Sorry - can't help it :D)

Well - as the title says i'm curious about how people spot their own mistakes while playing.
As for me i often have a hard time doing that - i often experience people patting my shoulder, saying "Why do you keep doing that - i see it coming, and i get you from doin' that!".

So i'm just curious - how is this like for the rest of you?

Regs