“Don't worry, be happy.”
Lord Meher http://www.lordmeher.org/index.jsp?pageBase=page.jsp&nextPage=6742, by Bhau Kalchuri, pp. 5770, 5970, 6742. The famous Bobby McFerrin song was based on this phrase often used by Meher Baba.
Variants:
Don't Worry; be Happy! Remember Me; I will help you.
As quoted in Showers of Grace (1984) by Bal Natu, p. 92
Do your best, then don't worry, be happy. Leave the rest to me.
As quoted in The Homeopathic Revolution : Why Famous People and Cultural Heroes Choose Homeopathy (2007) by Dana Ullman, p. 367.
General sources
Variant: Don't worry, be happy.
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Meher Baba 113
Indian mystic 1894–1969Related quotes

“Don't worry about failures, worry about the chances you miss when you don't even try.”
Source: Chicken Soup for the Soul

(Don't Worry) If There's a Hell Below, from Curtis (1970).
Song lyrics

“Don't worry that children never listen to you; worry that they are always watching you.”
As quoted in Reflections for Tending the Sacred Garden (2003) by Bonita Jean Zimmer, p. 182

“I don't know, man; don't worry about it.”
from "Broad Street Scientific," 2012 edition, quoted posthumously

“Pray, hope, and don't worry. Worry is useless. God is merciful and will hear your prayer.”

“But don't worry… only yours is right.”
Replying to a tweet stating "There are almost 5,000 gods being worshipped by humanity." https://twitter.com/zachbraff/status/254965828762624001