This alone I know, that I know nothing.
Doubt is not a very agreeable state, but certainty is a ridiculous one.
Philosophy begins when one learns to doubt - particularly to doubt one's cherished beliefs, one's dogmas and one's axioms.
We make all these plans about how things will turn out. But life happens. Plans change. So we doubt. We draw on strength we didn't know we had. We give up any allusions of control. And we deal head on with problems that come our way.
If you believe you can, or if you believe you can't, you're right
We can use doubt to self analyze. A measure of doubt can help us to attain self-honesty. But, like too much water, too much doubt will also destroy us.
Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason than that of blindfolded fear.