The source is likely to be either modern Buddhist monk Thich Nhat Hanh, or Calvinist clergyman Abraham Johannes Muste. The phrase appears in Thich Nhat Hanh's writings; but it also appears in a volume of US senate hearings from 1948, when Thich Nhat Hanh had not yet been ordained as a monk. Muste is known to have used a variant of the phrase – "'peace' is the way" in 1967, but this was not the first time he had used it, and he had a connection with the 1948 hearing.
Misattributed
“There is no way to happiness. Happiness is the way.”
Source: The Happiness Project: Or Why I Spent a Year Trying to Sing in the Morning, Clean My Closets, Fight Right, Read Aristotle, and Generally Have More Fun
“Allow children to be happy in their own way, for what better way will they find?”
“To be of use to the world is the only way to be happy.”
“The quickest way to happiness learning to be selfless.”
Source: Song Growing Up
“Happiness is doing it rotten your own way.”
I. Asimov: A Memoir (1994)
