Geez ever heard of a period OP? Your problem IS fixed by the "AFC" advice. The problem is you can't let go the idea that she IS the "one." Your brain becomes accustomed to thinking about someone else. Being addicted to their presence in your life. It expects it. As long as you continue to entertain these thoughts you are metaphorically holding onto the relationship and not "letting go." As they say in meditation, let all thoughts pass, both good and bad. Once you get in the habit of this with thoughts of her as the subject, your mind will start to let go of these thoughts instead of reminiscing over them. It's your only option. It's a skill. You can't become obsessed with her. Meditate and focus on other things in order to more easily let her go as a recurring thought. Your life should be involved enough you can't just daydream about her. Even when you're alone.