“Happiness is invisible and unfelt, when we don't know the meaning of gratitude and thankfulness.”
Related quotes

Original: Esistono persone che sanno ancora ringraziare. Grazie, una semplice parola che dimostra gratitudine, un gesto in estinzione.
Source: prevale.net

Reverence for Life (1969)

As quoted in "Bob Says 'They Try': Feeble Pitching Takes Joy From Clemente's Night" https://news.google.com/newspapers?id=hBFOAAAAIBAJ&sjid=h_0DAAAAIBAJ&pg=5612%2C2872741 by Charley Feeney, in The Pittsburgh Post-Gazette (Wednesday, May 17, 1967), p. 26
Baseball-related, <big><big>1960s</big></big>, <big>1967</big>

Last lines to all the artists present during the documentary concert, "A Tribute to Al Hurricane - The Godfather".

“I do not think that we have a “right” to happiness. If happiness happens, say thanks.”

Statement made to a correspondent in Paris in 1976 — reported in John Callcott, United Press International (December 21, 1982) "Arthur Rubinstein, At Age 95; Concert Pianist and Bon Vivant, Boston Globe.
Attributed

““Thank you very much, sir,” said Beth with nothing resembling actual gratitude.”
Prologue “The Minder” section 5 (p. 10)
The Republic of Thieves (2013)