My coach jumped in and said something really wise: "Well, yes - it's wonderful to aim for that level of familiarity…but don't let that make you feel like you have all the control. You never have ALL the control. So let's just give up that myth right now."
Brilliant. And true, you know? Even if I know a piece of text like the back of my hand, I can't control tech elements or my scene partners or my audience. Anything can happen, regardless of how much I rehearse something on my own. So, yes, I get that -- use my discipline and study my role to the best of my ability, but don't cling to all those hours of preparation as if they are some magical talisman that will make everything ok. I can't ever have complete control.
Truly - I have something bigger to remember tomorrow night. The sound tech is juggling a lot of tasks for the show, so he's asked me to remember to mute my own mic when I'm not on stage.