Changing your thoughts takes time and practise...and you need to be gentle on yourself! Helen Keller quotes:" Life is either a daring Adventure - or Not???? So if your are living on the edge, taking risks, overcoming challenges, making lifestyle changes, you may need a constant reminder to keep positive.
When you are reprogramming your thinking, you need to release the past. It's gone, you cant change any of your actions, so forgive yourself and others if you need to and begin to move forward.
Sometimes when you are changing your thoughts, it's not from negative to positive, it is about Choice A or Choice B.
Source: http://xtramsn.co.nz/businessandmoney/0,,13308-4012558,00.html