Maybe there's more involved than ordinary love. Some people can make a clean break from an ex and move smoothly into new relationships. Others spend every waking minute try to find ways to get back together with a person who has decided they're ready to move on. Within normal relationship endings, there are many periods of wishing the relationship was back on track. Eventually, you learn that the relationship is over, and you accept that it is over.
Obsessive love is different.
Thoughts of the lost love consume every waking moment. The other person becomes the center of the universe, the pivot point upon which everything within life revolves. Here are some resources regarding obsessive love. Love and Addiction From the Stanton Peele Addiction Web Site, an in-depth article about addictive love. Ask the Expert - Obsessive Love From MHi, the question and an answer.