The syllable "pra" in Prasanthi means expanding, enlarging. Santhi means peace.  So, Prasanthi means expanding peace, obtained by the absence of desire, anger, greed and hatred. This is the backbone of every individual, and for the spiritual aspirant, this is the very breath. Many feel that they have peace when some worldly desire that was vexing them is satisfied. That satisfaction is not real peace. It is but a temporary, short-lived interval between one worry and another...Prasanthi has no ups and downs; it cannot be partial in adversity and complete in prosperity. It cannot be one thing today and another tomorrow. Maintaining the same even flow of ananda (bliss) always, is Prasanthi (supreme peace).

-Divine Discourse, Prasanthi Vahini .

Those who are anxious to live in joy must always be doing good. - Baba