Who said "The only constant is getting let down."?

This quote is attributed to Droopy.

The only constant is getting let down. - Droopy

"The only constant is getting let down."

Droopy Change

"I'm so happy."

"Hello, I'm so glad to see you."

"That makes me so sad."

"I'm afraid I have some bad news."

"Change brings new opportunities."

"Every day is a new opportunity."

"Healing doesn't mean forgetting."

"You either get better or you get bitter."