Luck begins when something good or bad happens unexpectedly. When a succession of these events occur, we say we have a "string" of good or bad luck. Sometimes these events are truly random and sometimes they're not. Sometimes these events are merely breadcrumbs leading you on a pre-determined path in life, pre-determined by someone else.
On a grander scale, imagine putting together a scavenger hunt for a friend: Clues are put in pre-determined locations. The clues provide information (or cause action) that will lead your friend to the next clue. Finally, the last clue gets your friend where you want them. The clues are deliberately put together and tuned so your friend will understand them (i.e., you wouldn't write them in Italian if your friend didn't know Italian).
Have you ever had a string of luck bring you to an amazingly good or bad outcome? Did the string of luck impact someone else more than you? If so, consider that your supposed string of luck — good or bad — was merely the catalyst that would affect someone else.
Those with their full polarity will create events for others — often incorrectly labeled good and bad luck — to bring about outcomes to achieve goals in very roundabout ways.