One could say that doing the same thing over and over and expecting a different result is the definition of practice. I've heard that sometimes it does work out that way, but I can't claim much personal experience of such. I've managed to get more consistent at producing bad results a few times.
Sometimes we laud people for trying the same thing over and over - especially if they eventually get a different result - until that happens we call them crazy but then they're labelled persistent.
When the discussion of the this first arose on the board years ago I was of the same opinion as Elindholm - that it didn't seem to be the kind of thing Einstein would say. I did an internet search and found it quite widely attributed to him - and didn't find a substantiated attribution to anyone, Einstein or some other body.
Suppose that you have an experiment with an outcome you believe is not 'deterministic' (at least is in terms of the variables you can control). Your best guess is that the experiment has a 5% chance of success in each trial. Clearly, quitting after 1 failed trial is lack of persistence and continuing after 1000 failures is wacky... so at what point does the cross over from persistent to insane occur?