Michael McCullough, professor of psychology at the University of Miami, along with Robert Emmons, professor of psychology at the University of California, presented a scientific study in 2003 that examined the effect of a grateful outlook in human beings.
McCullough and Emmons asked several adults to keep a journal. They were to record their thoughts, experiences, desires, etc. A group of them wrote about their daily routine. Another group talked about unpleasant events that had happened to them; on the other hand, the third group wrote a list of things they were grateful for.
Curiously, those who were concentrated in the gratitude they felt towards others were the ones with higher levels of energy among the group of participants in the study. This individuals were the ones who spent more time practicing sports, enjoyed higher quality of sleep and higher immunity against illnesses.
Having this in mind, I invite you to develop the power of gratitude. Start a gratitude log in which you write each day five things you are grateful for.