Is it luck or common mistake ?

Wich one of you  didn't mate by chance?... , maybe i was so stupid to see it coming through but it's not only about mate because it happens all the time for example when you find your pieces in the perfect location to block the opponent master plan i'm talking about how sometimes the opponent makes his move and somehow it's like all the pieces were waiting for that move to nail him i'm not interested  in common mistakes but they are related and that's counted as luck too but i'm more concerned about pure luck that finishing blow that comes from outta no where :D

yes. It happens. Not by design but by chance. But GMs don't leave anything to chance! There in lies their greatness,!