I have read that you should look at what is "bringing you down" acknowledge it and then LET IT GO! Your body keeps bringing up the negative because it wants it to be acknowledged and they you can release it and more positive happy thoughts will come up and stick.
You may also want to look into your diet. You may be low on certain vitamins and enzymes that are causing your system to be pulled down. I would recommend the book The Diet Cure by: Julia Ross
