If you know you made a mistake, ask to patch it up. Otherwise you'll be hearing that mistake every time you listen to the track.
Once you've done your bits, it can get boring very quickly. Take something to amuse yourself with.
Studios are like a microscope. Don't over analyse (else you may loose the vibe, and that goes for everyone). Studio recording is very different to live, so accept it and work at it.
At midnight, when the mix is sounding good, if anyone says "can I have a bit more me", tell them "no" in the sternest terms, else you'll be the at 6 in the morning thinking what the hell just happened! (trust me, I've been there with bands too many times)
Don't try to do too much, be realistic, things take longer than you think.
Enjoy it!