"Man suffers from two types of ills, physical and mental, the one caused by the disequilibrium of the three tempers of Wind, Bile and Phlegm and the other caused by the disequilibrium of the three Attributes—Pure, Passion and Dull. One peculiar fact about these two types of illnesses is that the cultivation of virtue cures both. Physical health is a prerequisite for mental health and mental health ensures physical health! An attitude of generosity, of fortitude in the presence of sorrow and loss, a spirit of enthusiasm to do good, to be of service to the best one’s capacity—these build up the mind as well as the body. The very joy derived from service reacts on the body and makes you free from disease." 

...Sathya Sai Baba, “The Temple” Discourse 9 September 1959
http://www.sssbpt.info/ssspeaks/volume01/sss01-23.pdf                          

"Everyone should have the conviction that wherever he may render service and whomsoever he may serve, he is rendering service to God because God is omnipresent. Such service alone is true sadhana."

...Sathya Sai Baba, “Share in Bhagavan’s Love” Discourse 24 November 1990
 http://www.sssbpt.info/ssspeaks/volume23/sss23-35.pdf