Bob Marley, although before I checked Google search, Books, and Scholar, I had expected to find it was by Epictetus. Oh well.
EDIT: In my defense, Garvey's original is not the same as the Bob Marley version which Robin presented. I think it's a little disingenuous to consider the Bob Marley version 'misattributed'.
Take off every 'quote'! You know what you doing. For great insight. Move 'quote'.
And if you don't: