You have to assume things. I assume there is solid ground under my desk chair. I don't stare at the ground nonstop for confirmation.
I assume my family loves me. I don't act like an insecure teenager and seek confirmation every day.
I assume the people around me act in good faith unless demonstrated otherwise. That way I don't come off as a paranoid bastard.
I assume my car will start, my PC will boot, and my health will continue to be good. I can't function otherwise.
Sometimes I make an ass of myself and others. It's better than being stodgy and difficult.