I guess that if I was that scared I would take a bus. You don't have to ride a bike if you don't like it! Before giving up, you might want to take some lessons or just ride with someone who is a bit more experienced at riding in traffic and get some pointers. It really doesn't have to be frightening.
That said, I do sometimes find myself in scary situations. You must stay calm enough to think and ride your way out of these situations. Can you change your route or the time that you ride, just temporarily until you get your nerve back?