The stuff that we're doing on set, the stuff that fills our life with meaning?
It really ain't that important. Seriously.
Sure we move people. But we're not firefighters, or heart surgeons. What we do is mostly fluff. It's entertainment. Entertainment that makes some people, and hopefully ourselves, a shit-ton of money.
I'm not saying that what we don isn't important, but lets' put it into perspective.
In general, no one is going to lose their life if we mess up a take (nod to the stunt men, for whom this may not be true). It's just another take. Now, once you get past the 3rd or 4th take, you may start costing people money, and by the time you're on take 10, they're wondering what the hell is going on. But still, no one's life is at stake.
What we is important, in context. We all love out-takes, but you don't want the set to be a free-for all. And you don't want to be unprofessional.
Believe it or not, being more relaxed about the whole process will make you better as an actor. More relaxed = more emotion. More emotion = more dramatic takes.