“Contentment is...the root of all happiness.”

As quoted in Treasury of Spiritual Wisdom : A Collection of 10, 000 Powerful Quotations (2003) by Andy Zubko, p. 71

Refuge Recovery (2014)

Source: Les Miserables

§ 2.42
Yoga Sutras of Patañjali

The Dalai Lama at Harvard: Lectures on the Buddhist Path to Peace (1988) by Jeffrey Hopkins.
Context: What is the Great Vehicle? What is the mode of procedure of the Bodhisattva path? We begin with the topic of the altruistic intention to achieve enlightenment in which one values others more than oneself. The Great Vehicle path requires the vast motivation of a Bodhisattva, who, not seeking just his or her welfare, takes on the burden of bringing about the welfare of all sentient beings. When a person generate this attitude, they enter within the Great Vehicle, and as long as it has not been generated, one cannot be counted among those of the Great Vehicle. This attitude really has great power; it, of course, is helpful for people practicing religion, but it also is helpful for those who are just concerned with the affairs of this lifetime. The root of happiness is altruism — the wish to be of service to others.

Gautama Buddha, Udana 10
Unclassified

Source: The Unabridged Journals of Sylvia Plath