Psychology Today - Meaning of Life Blog reports on a research study documents support for a widely held assumption about mental health.

People who felt most strongly that their lives were meaningful were roughly 40% less likely to die than people who felt most strongly that their lives were meaningless. Regardless of whether people were younger or older (within the range examined in this study), male or female, depressed or not, disabled or in full physical health, high or low income, white or any other race, well-educated or not, living a meaningful, purposeful life was associated with living longer.

Having meaning or purpose in one's life is fundamental to health. Without a reason to live, why would one put up with the difficult parts of life? Feelings of hopeless and helplessness can be successfully fended off by having a purpose and believing one can contribute. A meaningful life is what makes possible recovery from mental or physical illness, chemical dependency, great loss, or virtually any grave setback. Serving one's purpose is what makes it all worthwhile.

Having a meaningful life and peace of mind is what I believe is true happiness. As in Sheryl Crow's lyrics, happiness is "It's not having what you want, it's wanting what you've got." And indeed, it would appear that research supports that concept as well.