Until then, here's a quote I ran across that is so good I had to pass it along here:
…you cannot undo a mistake by continuing to make it. All you can do is stop making the mistake, cut your losses and move on.
The author is Bruce Bartlett, once Reagan's economic advisor. The topic really doesn't matter, since his insight applies to everything from wars and global crises to marriages and cooking, but if you want to see the original in context it's here.