According to this article from Woman's Day, saying thanks & expressing gratitude might make you healthier & happier.
To increase your health & happiness, visit this site each day. Let's Say Thanks is a program sponsored by Xerox. On the site, you are able to choose from a selection of post cards with images drawn by children around the country. You can type a message to be printed on the card you choose, along with your name and location. (You can submit a different card each day.) The submitted cards are printed and mailed in care packages to U.S. troops stationed overseas. These care packages are mailed by military support organization Give2TheTroops®.
Xerox is committed to helping people across the nation express their gratitude to our troops overseas. The launch of this program is aimed at reminding them how much Americans appreciate their service.