I've grudgingly come to admit that there's some luck in the world. A belief that luck doesn't exist is useful for getting a lot and developing a sense of internal control over one's life, but okay, there's random variables that hit.
A new definition of luck, then, is something like --
Luck: The outcome of variables outside of your control.
To reduce luck's impact on your life, you've got three options:
1. Increase your influence/control over events in your life.
2. Decrease the variables that matter to your end goal.
3. Or make outcomes less contingent on variables.
Of course, you can expose yourself to high-upside low-downside events, which will sometimes yield big positive results... while reducing luck's hold on you in the core areas.