Giving thanks helps you feel better.
Dr. Robert Emmons, professor of psychology at the University of California-Davis and the author of Thanks!: How the Science of Gratitude Can Make You Happier, has researched gratitude extensively. In one of his studies with psychology professor Michael E. McCullough of the University of Miami (reported in 2003), those who kept gratitude journals on a weekly basis exercised more regularly, reported fewer physical symptoms, felt better about their lives as a whole, and were more optimistic about the upcoming week compared to those who recorded hassles or neutral life events.
Other studies show that grateful people report higher levels of positive emotions, life satisfaction, vitality, optimism and lower levels of depression and stress. He has also demonstrated that grateful individuals place less importance on material goods; they are less likely to judge their own and others success in terms of possessions accumulated; they are less envious of wealthy persons; and are more likely to share their possessions with others relative to less grateful persons.
In other words, if you want to improve your happiness — give thanks — and do it daily.
The Psychology of Satisfaction and Happiness 