There is a ruthless yet simple way to forget about your ex forever that is based on Frankel’s paradoxical intention method.
It has two parts, both of which must be done; you must do the first part for at least a month. Set aside a time in your schedule when you are not doing anything else. Your task is to think about your ex as hard as possible from 8 to 9 PM, for example. Make yourself think about your ex exclusively for one hour every day with no days off. For at least four weeks, from 8 to 9 PM you should have no other chores, no invitations, nothing.
The other 23 hours a day, you must tear a dollar bill for each thought about your ex. Find 10 one-dollar bills and every time you have a thought about your ex in the remaining 23 hours, take one bill and tear it to pieces with relish repeating, “This is how my nerves are torn.” For each thought about the ex, tear up some money immediately. Once you’ve destroyed ten one-dollar bills, go on to five-dollar bills. “When I tear this bill, my nerves are torn exactly the same way if I think about him/her.” The next 10 bills should be 10-dollar ones, then 50-dollar ones, then 100-dollar ones. Most people don’t make it to 100-dollar bills, though.
For 23 hours you train your mind that there is a certain time dedicated to these thoughts. Any other time, you tear up money bills. Your mind cannot tolerate such treatment of money and will not lay itself open to it. On the other hand, making yourself think about an unpleasant person for a whole hour can really only be done for the first few days, after that normal life seems much more attractive. However, you have to make yourself remember your ex to the end of the experiment!
The technique will work if you do both parts at the same time. Set a clear time in your schedule. Set your alarm clock and make yourself think about your ex for just that hour from 8 to 9 PM, with no distractions. The other 23 hours, tear up dollar bills all the while repeating “My nerves are torn just like that.”
P.S. This technique works for getting rid of any type of obsession.