This is great advice. Modern cognitive science teaches us that the anxiety you are feeling is due to actual neural circuits in your brain. You've got to "desensitize" yourself to these circuits and build "confidence" circuits in their place. The main thing is to get started. Even if you ride just around the block, it's a start, and it will begin the process of building the right neural pathways in your brain. When you come back, reflect upon the success you just had and how good it felt. Gradually increase the distance you ride. Always try to end your ride on a high note. It may take some time, but eventually you will get your confidence back. Good luck!
Hang in there, restart slowly, just around the block, then around a dozen blocks, go with a group of friends and let them know of your apprehension. Or go on a mountain bike ride with easy trails or bike path--it is more stable and usually slower.