"The definition of insanity is doing the same thing over and over again, expecting different results."
So far, via various Web searches, I've found that quote attributed to Richard Bandler, Albert Einstein, Thomas Jefferson, and Rita Mae Brown. All of whom had/have brilliant minds, of course, but I still don't know yet who said it first.
Not that it really matters. They're still brilliant words to live by. What it boils down to is:
If what you're doing isn't getting you what you want, do something different!