Who said "The secret source of humor itself is not joy but sorrow."?

This quote is attributed to O. Henry.

The secret source of humor itself is not joy but sorrow. - O. Henry

"The secret source of humor itself is not joy but sorrow."

O. Henry Humor

Writer American 1862–1910

"Turn up the lights. I don't know what time it is."

"We are not made by our circumstances, we are made by our choices."

"Life is made up of sobs, sniffles, and smiles, with sniffles predominating."

"A stitch in time may have ten times the sequel."

"Never underestimate the power of a good laugh."

"Laughter is the best medicine."

"A good laugh is the best medicine."

"Laughter is contagious and wonderful."