Stress is a marksmanship-killer. It is estimated that the typical police officer loses up to 80% of his marksmanship skills during his first deadly-force encounter. Chances are excellent that you will lose that much, if not more, especially if you don’t practice enough. Even a small amount of stress can seriously reduce your marksmanship skills, as I have personally experienced. If someone is trying to kill you, you will experience very high stress.
One thing that the larger police departments have done that reduces that serious dropoff is simunitions training. Simunitions training involves the use of special reduced-load rounds in handguns that are manufactured or retrofitted for the reduced recoil. The participants wear full body armor, since there is still enough force to cause injury. Simunitions training gives the participant much of the real ‘feel’ of a gunfight, and takes out much of the !O!M!G!I’m!being!shot!at! response that has an impact on your marksmanship in a real gunfight.
Simunitions training, while very desirable, is something that few of us ever get. The next best thing is practice. LOTS of practice. You should practice your drawing from concealment even more than you practice actually shooting, and you should practice shooting a lot. One general guideline is that if you have practiced something 1000 times, then that’s the way you will do it under extreme stress. Somewhere around 1000 repetitions, you no longer have to think about what you have practiced.
Just be sure you practice the correct things.