According to the Life of the Elder Moses of Optina, a troubled monk visited the elder, seeking his counsel.
“Batiushka,” he said, “there is a thought that is bothering me a lot.”
“And what does your thought say to you, brother?” asked the elder.
The elder sat quietly and listened while the monk went on at some length about the remembrance of his failures and the taunting and accusing thoughts that weighed down his heart. Having heard the sad testimony, the elder finally spoke.
“My brother,” he said, “tell your thought that this is none of its business.”
Simple. Serenity suddenly settled over the monk, and he left the elder relieved.
I don’t know if you can use that, but it amused me.