Speak from thy own experience

"Speak from thy own experiences. though you won't be admired, you'll seldom be wrong."

I had written that quote on the back of a portrait I painted in 1964.  I have no idea where I found it.  But it was the sixties and you could find such sayings everywhere.  At the time, I was getting involved with artists and filmmakers – but you can read some of that in GRANDPA WAS A DEITY … I am curious as to the original source.