The quickest way to defuse fear or insecurity or anger is usually humor. I think comics figure that out quickly, and, once you figure it out, you think, 'Hey, if I can do this and get paid, that would be kind of cool.'
Above all, film is a business... Independence is a really cool thing as you can be a bit more bold, and take a few more chances with what you do.
I did a film once that I was killed in. It was a painful, horrifying day. It was a wonderful day from the standpoint of acting, but I was a wreck otherwise.