Don't repress doubt.
Rather, just on the contrary, watch, look deeply into it, analyze it. Don't leave any part of it unanalyzed, unknown. Become acquainted with all the layers of the doubting mind. That very acquaintance, the penetration into doubt, will dissolve doubt. One day suddenly you will awake one morning full of trust -- not as your decision. It cannot be a decision because trust is something you are born with; doubt is a learned thing. Trust is tacit, inborn.