It happens more often than people would think it does—the clock that doesn't stop ticking, the bill that hasn't been paid, bacteria that needs to be washed off from the hands, eyes blinking, everyday breathing made conscious, the cleanest room on earth, or a door lock checked one hundred times.
Inside, knocking at the head's door, there's an obsessive thought. You can open, but it won't come out. You can try to enclose it in a distant place, but it won't stop bothering. The obsessive thought's favorite activity is to knock and bother. It usually has no purpose. "Why is it knocking so much?" we may ask. "What does it want?" It only wants to bother, that's what obsessive thoughts do better.
Some obsessive people have this obsessive, worrying thought about them being the most obsessive beings on earth; some others are just too worried about something else. Because obsession is mainly related with worrying about irrelevant details made present by society and absorbed by an obsessive mind.
The obsessive mind is the machinery that makes possible for any thought to become an obsession. Obsessive thoughts, however, can be given a use; it's just a matter of selecting the proper obsessions. The obsessive idea of doing something useful; the obsessive idea of pursuing realistic goals; the obsessive idea of being the tidiest person on earth when it comes to discriminate between useful and useless actions, between realistic and unrealistic worlds.
The worst way to stop thoughts is to repress them. Anyone ever trying to repress an obsessive thought will find himself in a lot of trouble, as the thought will come back angry, knocking stronger—that's exactly how obsessions grow. So, instead of repressing thoughts, one can simply try replacing them. The new thought might become an obsession as well, but that's exactly when one can choose a useful obsession.
I had this obsessive thought I started feeding a while ago about my being capable of getting rid of all my obsessions. Unfortunately, obvious as it sounds, it ended up getting rid of itself.