I feel like the reason people get in their head is that people are looking for the proper thing as opposed to being in the thing.Heather Anne Campbell on the latest Pack Improv Podcast.
You’re supposed to be “in the moment,” to react with authenticity and without judgment, but you also can’t just say or do anything that comes to mind—there are rules, structures, ways of making your scene work better or worse, and you have to abide by those rules and structures while still at the same time seeming (and hopefully being) present and living fully within the moment. You’re supposed to establish who you are and where you are and why you’re there, but you’re not supposed to be clunky or overly expository about it. You’re supposed to find “the game” but still “be present” and engaged.
As veteran improvisers, without realizing it, we become severely limited by our own “good” scenic choices, and we start making them all the time. It’s at this point that improv stops being improv, and turns into a party trick. Before making these moves on stage, you may as well turn to the audience and say, “Hey, look what I can do!” while also turning to your scene partner and saying, “Hey, no matter what you say, I’m still going to do this!”