"Let sleep not come upon thy languid eyes
Before each daily action thou hast scann'd;
What's done amiss, what done, what left undone;
From first to last examine all, and then
Blame what is wrong in what is right rejoice."This was either a poem or a short saying of Pythogoras. It can be found in the Discourses of Epictetus, Chapter 10, Book 3.
http://classics.mit.edu/Epictetus/discourses.3.three.html