Sometimes it can be fun to look up a meditative principle on Wikpedia and see what it has to say. I did that with the word "gratitude" today. Here's an excerpt from the entry:
Research has also suggested that feelings of gratitude may be beneficial to subjective emotional well-being (Emmons & McCullough, 2003). For example, Watkins and colleagues (Watkins et al., 2003) had participants test a number of different gratitude exercises, such as thinking about a living person for whom they were grateful, writing about someone for whom they were grateful, and writing a letter to deliver to someone for whom they were grateful. Participants in the control condition were asked to describe their living room. Participant who engaged in a gratitude exercise showed increases in their experiences of positive emotion immediately after the exercise, and this effect was strongest for participants who were asked to think about a person for whom they were grateful. Participants who had grateful personalities to begin with showed the greatest benefit from these gratitude exercises. In people who are grateful in general, life events have little influence on experienced gratitude (McCullough, Tsang & Emmons, 2004).
Although gratitude is something that anyone can experience, some people seem to feel grateful more often than others. People who tend to experience gratitude more frequently than do others also tend to be happier, more helpful and forgiving, and less depressed than their less grateful counterparts (Kashdan, Uswatte, & Julian, 2006; McCullough, Emmons, & Tsang, 2002; Watkins, Woodward, Stone, & Kolts, 2003)
You can click through to the article and take a look at the footnotes if you want to know how to check out the research for yourself!