when you hesitate, it's actually that exact thing which causes all your actions to be less effective.
Always imagine the speaker on the stage: when you sense that he's not 100% sure in things he speaks about, he will never makes you believe in that, right?
Same with actions, if you are not sure that they are 100% right and correct, they are more likely to lead to some wrong results.

But oh well, that's only my personal beliefs