Toussaint: How did you know I have dry leprosy, that it isn’t contagious?
Papillon: I didn’t.

— Papillon

You have to take chances in life, or you will gain nothing. Most of the time when you do something, you will have most of the information you need. But every now and then, you will be forced to make a leap of faith. You may fail if you try, but you will never succeed if you do not. I think the trick in those circumstances is to know when something is important enough to make a blind stab, to have the skills and resources to deal with the consequences, and to not be surprised when presented with an unexpected result, good or bad.