stroke of luck
stroke of fortune

But in the end we had a stroke of luck.

And a real stroke of luck, that he should have known his weight exactly.

That was a stroke of luck, as it turned out.

If there is not stroke of luck, we are lost.

Or have we just had a stroke of bad luck?

What a stroke of luck to get another date with her!

I'm on the good side: I've never yet had a real stroke of bad luck.

But guess what it turned out that getting cut was a great stroke of luck.

We'd never have known anyone had been there except for a stroke of luck.

But in the last few days, we've had a stroke of luck.