Do you ever get really obsessed with something? I wager that everyone gets obsessed with something or someone at some point in their lives.
Obsessions are not always all bad. If you become obsessed with cleaning your kitchen perfectly, you may get it very clean. However, if you are so obsessed you can't get out of the house on time or to bed on time because you feel your kitchen has to be perfect — that's a problem.
Obsessive thoughts are a feature of obsessive compulsive disorder (OCD), and can also manifest in generalized anxiety disorder (GAD). Obsessive thoughts can also lead to compulsive behaviors like worrying about the door being locked so much that one has to lock it several times to relieve the obsessive thought.
In cases where feelings of shame or guilt are centered around compulsive thoughts, trying to "not" think the thoughts can actually make the obsession worse. This is due to a quirk in brain chemistry. By trying "not" to think the thought, it makes one's brain more aware of the thought and in turn makes it continue to think the thought.
When I'm feeling depressed/anxious, I often obsess over incidents of past mistakes and become overwhelmed with feelings of guilt and shame.
There are many ways to treat obsessive thoughts. For a detailed article, I recommend: How to Stop Obsessive Thoughts from CalmClinic.
That's all for now. Look for my next post on obsessions soon.