Write Down the Obsession
If you're wondering how to stop obsessive thoughts, the answer depends on just what your obsessions are. Sometimes, you may feel like your obsessions are taking over, and that you are no longer in control of them. The simple act of writing down your obsession can help you to identify it, and therefore deal with it. For example, if you are obsessing over whether you turned off the stove, you can write down "I am nervous that I forgot to turn off the stove," and then go check the stove to see if you turned it off. Check it thoroughly, make sure that you are positive it is off, and then add the sentence. "I am no longer nervous that I forgot to turn off the stove. The stove is definitely off." If you start to feel the obsessive need to check it a couple of minutes later, you can look down at the note you wrote and know that it is unnecessary.
Prove Yourself Wrong
At other times, writing down your obsession will not be sufficient because you may be unable to check that your obsession is false. For example, you are obsessing about the fact that you are going to fail an exam. In a situation like this, here's what you can do: First, write down the obsession and then try to think logically about it to see whether there are parts of it that are illogical. You might look at the worst case scenario, and realize that failing one exam will not change your life, and that you can always retake it if you need to. This strategy is one of the main ideas of Exposure Response Prevention (ERP), which is a technique used in Cognitive Behavioral Therapy (CBT). CBT is one of the main therapies that can treat OCD.
Take a Rain Check
If you cannot logically deal with your obsessive thoughts, schedule a specific time to deal with your obsessions. That way, when an obsessive thought pops into your head, you'll have a better "excuse" to give yourself for why you can't obsess right then. Just remind yourself that you'll be obsessing at a specific time later that day, and file away the obsessive thought for later. Trying not to think about a purple elephant in the room is near impossible, but filing the thought away seems safer and therefore easier to do.
Replace the Obsessions
If someone tells you to not think about a purple elephant in the room, you'll automatically think of one. So how can you figure out how to stop obsessive thoughts? Replace them with something else. Think of a happy memory from beginning to end, sing one of your favorite songs and really think about the words, do some exercise (or, if you're in public, focus on clenching and unclenching your fists – in your pockets, if necessary). These strategies can help you overwhelm your obsessive thoughts with other stimuli so that you can avoid obsessing.