I do believe in luck.
Some time if sth happens the way we wnt we say we r lucy.
For ex if same quetion come that we we learnt last minute we say luck.
if the interviewer asks questions we know we say luck.
Luck is just a word to describe when unexplainable good (or bad) happens. It works as a concept, but not in items, like so-called 'lucky rabbits feet'. Not lucky for the rabbit, eh?