Ride faster. When you are scared and ride too slowly, the bike wants to topple right over. When you get up a little speed, the bike is much more stable and easy to handle, much like a car. Just wear a helmet, old jeans that can get ripped up, and a long-sleeved shirt that you don't mind trashing if you fall. Hop on the bike, and pedal away, and don't go slow! I promise you will feel much more confident once you see how much easier it is to handle the bike when you are riding at a normal speed.