Perhaps the proliferation of negative thoughts is a reflection of your real-life situation. Were I in the situation you have described in other posts, I would be susceptible to the frequent intrusion of such thoughts, too.

Different folks have different advice for dealing with negative thoughts. Some like to fight them head-on with thought-stopping techniques. I prefer acknowledgement-and-release approaches (example from PC). All techniques have their limitations, though. May you find something that works, and may your circumstances improve.