Here is some very good advice that I found online! And I'm going to try it out myself!

A very effective way to eliminate negative thinking now is to use a tablet and write on it every negative thought that comes to mind quickly. Once your list is complete shred the paper and instruct your subconscious mind to allow only positive energy thought to enter. You will get very good at deleting the negative thoughts and eliminating them for good. But be sure to always replace them with positive energy thoughts or the old ones will try creep back into your life.