Self-defense is not about just knowing how to shoot. It is a mind set and physical ability. Training to shoot is absolutely a key component. However, leaning to be proficient with a handgun is far more that passing a License to Carry Class. It is about training yourself to be prepared. It is also about training yourself to be situational aware.
      I’m a guy who is well on the north side of middle age. I learned how to shoot when I was a kid. That means I could hit a stationary target without shooting myself or someone else. It didn’t mean I knew how to defend myself on my loved ones. I was trained as a police officer in the 1970’s at that time weapons qualification was one a year 100 rounds from 5 yards, 10 yards and 25 yards, standing in one place and shooting at a stationary target. In the Army qualification was also once a year, but again it was a test of self defense it was standing in one spot shooting at one target at various distances. None of these scenarios involved a great deal of physical exertion.
      I began self-defense training about a decade ago. I learned one thing really quick. I needed to get in shape. Self defense involves not only shooting, it also involves moving, and moving quickly. Situational awareness keeps you on your toes, but once you recognize a threat, you must deal with it. The first rule of gunfighting, is don’t get in one if you can get away from the threat, that means moving quickly. If you can’t get away from the threat and must counter, it then a golden rule is distance is your friend. To maintain distance, you must move quickly. An average bad guy can cover 21 feet in a blink of an eye. That means you must get off the mark, draw, and engage in that same blink of an eye. If your exercise regimen has consisted of working the remote or game console, you may very well loose the movement and distance game and thus loose the fight.
      Maintaining an exercise regimen doesn’t mean training for a decathlon. It means maintaining a physical level of activity that helps your body cope with stress and rapid short movements. How you do that is determined by your age and your level of fitness. If you’re my age the way your exercise will be different than when I was in my 20’s or 30’s. It will, however, help me maintain cardiac stamina, agility and strength.
     It is never to late to begin to train your body and your mind to react to a threat situation. Start small and build up over time. This isn’t a one-time thing to get to a certain level then quit. As you age, your physical abilities will change, you must continue a regimen that allows you to stay fit to fight for your lifetime.  

The best way to improve what you do on the range; drawing, firing, reloading and, most important of all, hitting the target in a timely manner is accomplished with what you do OFF THE RANGE. I know, dry fire practice is boring  - it is also vitally important. Here are a couple things you can do off the range that will improve speed and accuracy on the range.  
 
First insure all handguns and magazines are unloaded and the ammunition is in a different room. Check twice to make the chamber is clear. Lock the slide back and visually and physically inspect the chamber to insure there is no round in the chamber. After doing this, and only after doing this are you ready to begin your dry fire practice. 

First, practice drawing your firearm and bringing it onto target. your goal should be to identify your target and bring the firearm onto target in 2 seconds.  It isn't just about how fast you can get the weapon out of the holster, though that is important, you can be the fastest draw in the west, but if you are not bring it accurately onto your target speed doesn't mean squat. So, as I believe Wyatt Earp once opined, you want "to be slow quickly." SO, begin by practicing slowly and let you muscle memory dictate your speed. As your body become more familiar with what goes into presentation and accurate shot placement you will notice that speed begins to improve. 

It is'n a matter of practicing this a couple time a day. I would suggest that you do it 50 times a day - every day. And remember it is practice that makes perfect, it is perfect practice that make perfect, so don't cut corners, do it right  and don't rush it. Let your body dictate on how fast you go at first. one you get the muscle memory down, you can begin to challenge yourself on speeding it up. 

Stay safe on and off the range. 
"Chief"   

      Any learned skill is perishable. The only way to maintain that skill is through practice. So, how often should you practice. That depends, most of us aren't professional shooters. Most of us need to be proficient enough to defend ourselves and our families. There are specific skills each person needs to hone in order to be proficient in self defense. 
      The first of those skills is being able to hit what we aim at, that calls for practice. the majority of self defense events occur within 15 yards, often closer.  With that in mind, the majority of a person's training should occur between 3 yards to fifteen yards. An individual needs to be able to present the weapon, under any conditions, and successfully engage a threat and disable the threat at those distances. this requires several tasks done in quick succession.
      The first task is the presentation. A person should be able to draw the pistol from concealment within 2 seconds and accurately engage the threat. 
       The second task is to acquire the threat  and engage it as to eliminate the threat.
       The third task is to insure that all threats have been eliminated. 
       Finally, the last task is to secure your own weapon and notify the authorities.
All that sounds pretty simple, and it is; if you are prepared and that is why training and practice is essential for your safety. Failure to train is actually planning to fail. 
      Once most people have learned the basics of pistol safety and operation, the learning and honing of of self defense techniques is not complicated. regular practice of once a week should be sufficient to maintain your skills with confidence. We aren't training to be spec-ops operators or ninjas, we train to be prepared.   So, set time aside each week to practice the three tasks of defending yourself; learn quick presentation, quickly acquire the target and neutralize it, then insure no further threats exist.