Reason #631 Not to talk about an exam

Because you will only freak out about it and feel worse.
Go, try it. Go up to one of your classmates and start talking about the exam. How do you feel? Shitty? Yea, that sounds about right. Oh, he noticed that you had your palm squarely planted on your head as you were clearly angrily shaking you head halfway through? You totally want to be reminded of that wonderful moment.

Sometimes the only thing left to do is keep you mouth (and ears) shut and cross your figures. You are not going to do any better after the fact. Commiserating doesn't help.