You should try something that you KNOW isn't right.
Make a choice that your POSITIVE doesn't work for the scene.
Make the character a clown, a drunk, a 5-year old, a frikkin' cowboy, hell, a creep child molester priest, I don't care. Make some REALLY BIG, even random, choices and go all the way with them, total caricature, SNL style.
Guess what's gonna happen?
You're gonna have a little fun. You're gonna loosen the fuck up. You're going to take the pressure off because there's no way that the character would be this way.
Guess what else is going to happen?
You're going to get insight into the scene. Sure, you'll probably never play the scene that way at an audition, or on stage, or on set. But doing so opens you to more possibilities for the scene, and keeps you from getting in a rut. You know that rut where you're saying the lines the EXACT SAME WAY only at different volume? Yeah. That's not acting. That's boring.
And those things that you were SO sure were true about the character? Maybe there's a little wiggle room there.