The most common obsessions people have are intrusive thoughts about harm coming to themselves or loved ones, contamination from germs or dirt, and things being out of place or not symmetrical. These obsessive thoughts can cause severe discomfort and lead to compulsive behaviors such as hand-washing rituals, checking locks on doors for hours on end, arranging objects over and over again until they’re “just right,” or hoarding possessions in fear that they might need them later.