I made a habit out of reviewing my gratitudes in bed twice a day - just before going to sleep and on waking. It took a few weeks to make it a habit. I not only enjoy doing it, it makes for more relaxed sleep and also I noticed after a month of doing it that I automatically start looking for things I am grateful for during down time in the day. Cool bonus! In addition my life has been flowing smoothly and I think this is partly due to focusing more on what I am grateful for than what is "wrong". I am happier too.

PS If you are in San Francisco check out Cafe Gratitude - all the dishes have positive names like I am Happy, I am Abundant so you get to say that when you order. Then when the server delivers they say You are Happy, You are Abundant. The food it really tasty and healthy raw food that is like no other raw food and salads you have eaten before. They have a recipe book ("I am grateful") if you can't get there in person and want to get a flavor of the place from somewhere else.