It's spurious. This self-help piece from 1991 by the motivational speaker Stephen Covey is the earliest source to which I've been able to trace it, but it may not be him that invented it.

(Purely as a bit of pedantry, of course we don't have any real Socrates quotes, since he didn't write anything and we don't have any sources for his words that carry any likelihood of accuracy. But I suppose "Socrates" can equate to "Plato's depiction of Socrates".)