Exhausted after playing 5 matches
Nah i wanna play 5 more
I'm beat after one, and about catatonic after two... still I'll play if I can.
If you haven't played in a con setting before, know that it's the best chance to get in a few games against people you don't usually get to play, see play styles that might inspire you, and learn new and interesting ways to use existing spells and mages.
One example: I had never used, or played against anyone who used, Jinx before seeing it used amazingly well at a GenCon a few years back. It really made me rethink that spell, which seemed to me before that to be a simple waste of mana.