I learned discipline from my father. Not in terms of corporal punishment, but being determined in whatever you do, and sticking with it.
I have a discipline that has served me very well in my career and in my personal life... and that's gotten stronger as I've gotten older. I've always felt if I don't just have a natural knack for it, I will just out-discipline the competition if I have to -- work harder than anybody else.
I know there are actors we all want to beat up a little. I think it's important to do whatever it takes, and whatever it takes sometimes involves some physical or mental discipline. There's a lot at stake.