1) Hard Work is enabling factor for "luck", just like being born under the right circumstances is. Hard work does pay off, and thus it's valid to say "hard work helped me get here". What we're calling "luck" isn't a purely random roll of the dice. Working hard tilts the odds of good luck much further in your favor.
2) While Hard Work enables better statistical odds at the luck game, you have to be careful to understand that it's still just statistical odds in a luck game, and that structurally there can only be a small percentage of people who "win". If every single person worked equally (very) hard, the luck advantage of working hard would diminish to zero, and only luck (remember we're ignore other factors like wealth/coercion) would remain to differentiate the small percentage of winners. Because wealth is pretty much defined as having more than someone else (or else pricing/inflation will just readjust everyone back to the norm), not everyone can have more than the average. This is what blows a hole in the idea that anyone can work hard in order to achieve success. Anyone can work hard to increase their odds, but the odds are small without other advantages, and many may work hard and still fail.