Luck is the relation between random occurrences and one's values.
Random occurrences in favor of one's values are "good luck" and random occurrences against one's values are "bad luck". The less probable the event the higher the "luck" is. When the event is fully predictable in under one's control the term "luck" no longer applies to the situation.
For example: If you walk in the street and an envelope full of money lands on your head - that is good luck. It is a random occurrence that you happened to be at that place at that specific time and the relation to your values is positive since money is a value.
If you win every single game you play in a gambling place that is an extremely good luck - but again, it is all random (putting aside whatever brain was required to win the games). What makes it "extremely good luck" is the relative rarity of the events (the length of the winning streak).
I think that people see "luck" as an actual spiritual entity, as some form of liquid running in one man's body at some time. Evaluations like "This man is lucky" tend to mean that the man himself actually has some quality about him that affects events around him. In fact, no man can be lucky in that sense. Such a concept is mystical.
The reality is that some people have more random occurrences in their favor than their disfavor and this changes nothing of the fact that random occurrences are random occurrences.
Wishing someone "good luck" is no more than letting them know that you wish them success, that you wish the conditions they would encounter outside their control would be in their favor.
So if you are feeling lucky, punk, better check your premises. A feeling of "luck" is not reality based, one cannot "feel" future occurrences outside one's control. :)