The heart is strong. Eventually it'll heal and if he isn't the one, your heart will help you find the right one. If you let it, of course.
Well... It's not a stupid threat at all. I can relate. I was with my girl for 5 years. Known her since '06. After a 5 year relationship with the girl I was close to marrying, I cheated on her on a night out drinking with friends and then broke up with her after confessing. She still chats with me every now and then but it's sad to think someone you once talked to every day for 5 years, and was close to marrying, now doesn't want anything to do with you. It's hard to move on knowing you are 100% at fault and I dont think you ever stop loving them. But oh well. Fuck it.