Here’s great story about Katharine Hepburn.
Excerpt from Sidney Lumet’s Making Movies:
Sidney Lumet:
At the end of rehearsal [for Long Day’s Journey], just before shooting, I gathered the actors to tell them about my shooting system and habits and to find out if there was anything they needed during shooting that we could provide. At this session, I said to them, “And by the way, you’re all invited to rushes.”
As we were leaving, Kate called me aside. “Sidney,” she said, “I’ve gone to rushes of practically every picture I’ve ever made. But I won’t be coming to these rushes. I can see how you work. I know Boris’s work [Boris Kaufman was the cameraman]. You’re both dead honest. You can’t protect me. If I go to rushes, all that I’ll see is this” — and she reached under her chin and pinched the slightly sagging flesh — “and this” — she did the same thing under her arms — “and I need all my strength and concentration just to play this part.”
Tears sprang to my eyes.
I’d never seen an actor with such self-knowledge and such dedication, trust, and bravery.
She was breaking habits of thirty years because she knew they would interfere with the job. That’s a giant.