Gratitude is the healthiest of all human emotions. The more you express gratitude for what you have, the more likely you will have even more to express gratitude for.
Just before I go to sleep at night, I spend some time running through my list of thank you's ... it's a fabulous way to fall asleep. And on those nights when I have trouble sleeping, I count my blessings even more, and for longer. The more I can say thank you for the things I have, the less I worry about those things I don't.