No man is a failure who is enjoying life.

William Feather (1889-1981) American publisher, author

(Attributed)

Widely attributed to Feather (e.g. Laurence Peter, Peter's Quotations (1977)), but no citation to be found online. A particularly common quote (usually without attribution) in school yearbooks, collections of wisdom / happiness quotations, etc.The earliest use of it that I can find is as anonymous column filler in The Deaf-Mutes' Journal, Vol. 61, No. 50 (1932-12-15).

A variant adds "No man is a success who isn't."