“ If in your head you undertake hatha yoga as a form of exercise or body building, you will end up with just what you reached for ... a more beautiful body. On the other hand, if you undertake hatha yoga as a form of yoga then it will, in a relatively short time, bring about a profound metamorphosis in your body calmness, sensitivity, and lightness ... all of which will facilitate your sadhana. ” - Ram Dass

Research.  Stages/Tasks.  Vaillant.  Kohlberg.  Adult "maturation tasks".  Retirement.  Death.