It’s pretty long, and it’s chock-full of useful tidbits. Go read the full post if you haven’t already (I know you have, but go re-read it).
Closely related to this question is the “I just had a terrible class/practice/show and I’m in a rut and what should I do?”
I have a few different mantras I run through in my head. One is “listen and react.” I tell myself to forget everything else and just obey that rule. This is an effort to keep it simple, but to still be participatory.
Another one is I’ll tell myself “be playful.” This was advice my brother gave me before we did a two-prov set. It was the first time we had performed at a particular theatre and we wanted to be good. He grabbed both of my shoulders and looked at me and said “be playful — you’re good when you’re playful” and it freed me of worrying about being “good” or doing it “right.”
…How long have you been doing improv? Is it less than a year? Then “being in your head” is just part of learning something new. You can’t avoid it. You wouldn’t expect to be able to sit at a piano and improvise beautiful songs after just ten months of lessons. Yet improv students seem to get frustrated if, during their first year of study, they find it difficult. You understand that to learn something means to go through a period in which you are clumsy at it, right? Well, maybe you’re just in one of those necessary phases of being clumsy. Rest easy: you are growing more powerful.