I don't know about you, but when I first went into record at a pro studio. I was very nervous .. luckily the engineer was awesome.  Got us to forget about the record button.  I know I used to be able to come up with some killer riff or lead thing, then f it all up when I hit the record button.    the key thing is to practice it till you have it down so well you can play it without thinking about it.. (that helps) or make sure you are giving yourself enough space (area) and time (before the actual recording starts up)  I like to  use a 4 bar pre-roll  and sometimes even a 8 bar pre-roll just to get settled and ready to go. 

 when I do punch-in (if needed),  I tend to start the song quite a ways back before the punch-in,  and just start groovin with the music,  not worry about what the computer is doing.  Just what I am doing musically .

 Relax, relax relax, and breath.

I'd love to be able to punch in like a guitarist (I record drums). I have to keep playing a song until there's a sizeable break where I can drop out, and there are some songs where I have to knock the whole thing out in one take. So yeah, relaxation and knowing your parts in your sleep is key!

sometimes it pays just to keep the record button on all the time and then delete what you don't want afterwards.  it's not too hard these days to do that either.