Crawling Out

Do you ever find yourself in the midst of negative thinking about persons or situations?  I do.  And when I am there I cannot seem to stop the negative thinking just by wanting to stop.  Ever so slowly I begin to crawl out of my mind, and it does seem to be as helpless as crawling.  I just cannot simply stop altogether.  I say, "OK, stop thinking so judgmentally about that person. " But very soon thereafter, I am thinking badly about some situation be it work or community or relationship.  What works best for me in these moments is to focus on doing one thing that will occupy my mind.  Type out a blog.  It has to be something that really does take up my mind.  Cleaning my room won't do it.  My mind is still to free to be thinking other things while I am doing this chore.  What solutions do you have when negative thinking holds you hostage?