When I make a move, I usually have a reason to do so. The reason may proove to be faulty. But the move may still be good for a different reason. That's luck.
If there where no luck involved when playing chess, a stronger player whould always perform better against a weaker player. Because there is some luck involved, a stronger player often performs better against a weaker player
Some players when they loose... they say thay had a bad luck game today... what do you think?