In a word... yep. I dont know if it's the "only" thing but it's certainly the main thing. Training training training which is mostly repetition repetition repetition. As former martial arts instructor I can tell you that in most marital arts schools, even at the most advanced levels you are still required to practice very basic offensive and defensive moves over and over and over again even though you've been doing them for years. The reason for this is not because the instructor is afraid you'll forget how to perform basic movements but rather that because if you repeat the same reaction litterally thousands of times, then eventually if becomes almost automatic. Positive target identification (and a bazillion other things) can be trained in the same way.