Luck. Definition: "a purposeless, unpredictable and uncontrollable force that shapes events favorably or unfavorably for an individual, group or cause." - Wikipedia
I, for one, do not believe in luck. The above definition alone is reason enough not to. Purposeless, unpredictable, uncontrollable; these words go against every grain of my being. I feel it is pertinent to live one's life with a firm sense of purpose. I believe in predictability, in schedules, in a plan, in order. While there are elements of our lives that are uncontrollable, I think that there are many things in our control. In life we need to take that control over our lives.
I don't believe in the notion of luck because I believe very strongly that we make our own way. Meaning that it is not some arbitrary, uncontrollable, outside force, but instead one found within each of us. The notion of luck can be misleading, allowing us to think that maybe we'll "get lucky" perhaps, or that it'll be "just our luck." This causes us to have a false sense of control over our own actions and decisions.
I choose instead to believe that when you know your purpose, predict the course you would like to take and have control over the choices and decisions you make (within your control) that you will meet instances in your life that are "lucky." However, these instances have nothing to do with the above definition and everything to do with how we each choose to live our lives.
Some may argue, "What about the times that are truly unexplainable?" For instance, winning the lottery or being upgraded on a flight randomly. In both of these instances I would argue that it is not luck at play at all, but instead a combination of purpose, predictability and control. Take for instance the person who wins at the lottery. That person purposefully went to the store and bought a ticket. That person predicted what numbers would be good, which game to play or the gamble with the best payout -- and took a chance on one to (hopefully) become a winner. Lastly, that person was in complete control of their decision. They would have never won if they had never played.
Luck is not a word in my vocabulary not only for all of the above reasons, but also because if something fortuitous and unexpected happens I would much rather attribute it to the actions I've taken in life. Think about your belief in luck, reevaluate and see if you instead decide to just have a belief in yourself and creating your own path, whatever that means to you. Own your personal lucky, for it is not arbitrary.