Sometimes your body language is enough for an actor to know that you're not happy. And you don't really need to say it out loud if you deal with actors you know very well. And I don't think you really need to be explicit. ↗
You can't stop the aging process. There's only so much oil you can put on your body. I've always just tried to go with my age. If the part requires somebody a little younger or older, I can probably get away with that. ↗
You have to contort your body in a certain way to hit a low note. When you're on film, you can't. So you do, in a sense, get to hide behind your voice, which is nice. ↗