it is so hard to do, but honestly, the best thing is to just forget about an exam once you've taken it and focus on what you have left to do. one of my 1L professors gave some really great advice - he said an "a" exam answer generally only addresses about 60% of all possible issues. no one is going to get everything! so i really wouldn't beat yourself up too much about stuff that pops into your head after the fact. i'm sure you will hear this a lot, but many of the exams that i felt like i totally bombed actually wound up being my best grades in that semester. seriously though, once you've taken an exam, don't think about it too much. it will just distract you from everything else you have to do, and stress you out.