If I have enough ego to say I'm a writer, a director, a producer, and an actor, I should have the energy and the knowledge to write a scene for this great actor named Henry Fonda and direct him in it and have it work.
I'm a very lazy person by nature. I have to be really engaged, and then I go straight from lazy to obsessive. I couldn't study chemistry, but I could memorize all the books for Dungeons and Dragons. It was ridiculous. The trick is to find what I like to do.