Can you explain this quote luck is what happens when preparation meets opportunity?

I believe this quote comes from Oprah Winfrey. She is saying that if you're prepared for an opportunity when it comes along then that is her definition of luck. Really there is no by chance "luck" unless you make your own. To get "lucky" you must not just sit around unprepared and wait for something to magically happen or to come to you. You have to make it happen. In order to make it happen- you have to do the leg work and prepare yourself for it. (Example: if you wanted to get a book published and you never finished that book- then it's never going to get published. But if you write the book and then by chance meet a book publisher or if you send it out to agents to be published- and someone actually wants to publish it- then you're prepared for the opportunity to have it published.)