Luck is an interesting word, usually used to define positive or negative events that happen, seemingly outside one's control. Let's see its official definition: success or failure apparently brought by chance rather than through one's own actions. Here is another: the phenomenon and belief that defines the experience of notably positive, negative or improbable events. As clearly stated, these definitions completely clear you of any responsibility. Your actions are seen as useless or inadequate towards an unknown 'power' that decides for you. So, it's either 'chance' or a mysterious 'phenomenon' that chooses for you. This means that, if you have setbacks in your life, the fact that you resolved to make important decisions in a certain way has nothing to do with the results you get. That's an easy way out, with no need for responsibility, isn' it?
P.S. No reference to gambling, which can be considered the easiest way to knowingly create one's own ruin. *