Get rid of this annoying mania (and depending on the person - this is a real mania) is very difficult. The first thing to realize there is a problem you have to understand its roots and causes of development. Then you must determine for itself that the relationship - it is not a sentence and not as scary as it seems. And then begin treatment.
If possible, consult a psychologist. But do not be lazy, start working on yourself. To start translate their interests in a slightly different plane from those of a loved one. You should see different hobbies. It only play a positive role in the development of your relationship - you will have something to discuss something to boast, etc.
Another step - to meet more often with my friends. Evening, day, and morning gatherings in a cafe with a cup of coffee very vigorously, elevate mood and lets you feel the full personality, the ability to think and act for themselves.
Change something in your life dramatically. For example, to change a job, go to college to get a second or third degree, make major repairs in the house. All this for a while you will pull out from the abyss of routine will see new life, meet new people and teach them not only to look at him only.
If you broke up, and the dependence remains, it is necessary to fight the same way. Just add more to get rid of all his things. It is not necessary to store here "this shirt in which he was that day." All this is only reopen old wounds and prevents you from moving forward. Remember that the best thing to get rid of dependence on the person - it is self-cultivation. But do not develop only temporarily, to a meeting with the next prince. Once recovered from addiction, do not give yourself more time to get into it.