You can make decisions in the face of uncertainty based on an assessment of the risk and the probabilities of the possible outcomes. If you get in your car you put your seatbelt on without knowing whether you're going to need it for that particular ride. There's no need to "pick a side" on the question of whether you're going to have an accident on that ride. Being uncertain about something is almost the opposite of cognitive dissonance, which comes from being quite certain about contradictory propositions.