Been saving this one so I could answer it properly.
My personal working theory is that there's multiple different kinds of luck. There's the harder you work, The luckier you get sort, which I suspect is what most people think are thinking of when they speak of luck.
Then there's the sort of luck that Kipling mentions:
When first under fire an' you're wishful to duck,
Don't look nor take'eed at the man that is struck,
Be thankful you're livin', and trust to your luck
And march to your front like a soldier.
Had a friend who'd spent some time in interesting places, on one occasion he broke left when his buddy broke right. He got a Silver Star and his buddy got shipped home in a box, that sort of luck. I just call it the gods of probability and try not to offend them.
The last kind of luck I only know of from personal experience, I consider myself lucky because I have a knack for doing just the right thing except for all the wrong reasons. Can't think of a good example offhand but I end up getting credit for a bunch of stuff that was never my intent.