http://www.spring.org.uk/2011/10/8-ironic-effects-of-thought-suppression.php

Suppressing unwanted thoughts and feeling according to this PsyBlog doesn’t work. Psychologists have known for a long time that the brain doesn’t process negatives. I call this the blue tree syndrome because when I tell you ‘don’t think of a blue tree’ in order to not think it, you have to think it first, then discount it. Funny that!

So often clients I work with who have anxious or negative thinking patterns try so hard to not have the thoughts, that paradoxically it makes them stronger! Negative thinking usually serves a purpose at an unconscious level; often this is to protect us from what might happen. When we begin working together and clients start to listen and understand this positive intention behind the negative thoughts, the thoughts can transform into something more useful and the need for you to be pestered by them, because you are not listening ceases, to exist.

So instead of desperately trying to suppress negative thoughts, try listening to them and work out what needs to happen instead. By working with your mind, not against it, you can make a huge difference to the quality of chatter inside your head!