Recently, I was watching a martial arts movie called Brotherhood of Blades and there was an interesting line where the hidden villain says to one of the other bad guys, "Those who rely on luck are gamblers." That was an interesting line in that I felt was relevant to martial artists. Luck implies that there is some part of engaging our opponents which is completely random and out of our hands. While this might be true, this randomness is something a martial artist cannot afford to rely upon.
In gambling, there is no such thing as winning all the time which is probably true for martial arts as well. However, in the martial arts if one loses, they usually lose their life or the life of someone close to them. Therefore, one can see that any amount of error is unacceptable.
Since as martial artist we are not gamblers then we must be pragmatists in our outlooks. This practical way of thinking assumes that our challengers are working hard to defeat us and thus we must work harder. There is no substitute for hard work, planning and preparation. A saying that I like from Scientific American many years ago that I like is apropos, "You fail to the level of your preparation." Generally speaking, when one puts in the effort they are successful. If there is luck, then it is that sliver of an opening between two people who are both thoroughly prepared but most of us will rarely encounter that.
The philosopher Seneca said, "Luck is what happens when preparation meets opportunity." Since we cannot afford to gamble then it is best that we get started...