Since when do you ever look back and say that you wouldn't do anything differently? That indicates you haven't learned anything, not that it was bad luck.
I usually go by "If I look back and can honestly say I wouldn't do anything differently given the information I had at the time, then it's bad luck." That doesn't mean that I made the right choices, or that I'd make the same choices in the future. But it means that I did the best I could with the information I had available to me, and didn't have any rational basis for choosing differently.
