An intellectual understanding of your balance point on a bicycle will not necessarily make you a better rider only good physical autonomic responses will do that and those, fortunately, can be trained.
Find a big empty parking lot or paved space where you know you will not be bothered by cars or other kinds of traffic or distractions. Make sure you are wearing a helmet and at least cycling gloves, if not the kind of elbow pads, knee pads and wrist guards that skateboarders or in-line skaters wear. Find conditions like you are currently insecure around and build up to those challenges by slowing tackling them in increments. Your body will begin to understand faster than your mind will, if you let it, and soon you'll be confidently riding where once you felt hesitant.