One of my sons is a commercial pilot, and one of the first sayings he was taught as a novice in flight training was, “Remember, altitude is your friend. More is better.” It’s simple physics: The closer you are to the ground, the less time you have to deal with a problem.

Those of us who carry firearms should adopt a similar mindset: “Distance is our friend.” Because the closer we allow a predator to get, the less time we will have to react. And over the years, I have seen many such cases, with the results seldom being good — and sometimes even fatal.

Keeping at a safe distance seems like common sense, but what constitutes a “safe distance,” anyway? The famous Tueller Drill (or “21-Foot Rule”) is based on the idea that in general, a young, strong assailant can close that distance in less than 2 seconds, which is less time than it takes the average person to draw a gun.

But such drills do not take into account a whole host of variables. For instance, what kind of clothing are you wearing? Drawing a gun from underneath a heavy coat in Minnesota in January is nothing like retrieving a gun from beneath an open shirt in Florida in June.

The same goes for your method of carry. It is simply a reality that some are “quicker” than others; someone open carrying with a belt slide holster will be faster than a person drawing from an IWB rig concealed under heavy clothing.

And in many climates, both your clothing and your method of carry might involve one way in summer, and another in winter. This is precisely why we strongly recommend that you consistently practice drawing your firearm and using your usual carry rig dressed exactly as you normally do while carrying.

However, none of the above will matter if you are not following the number one rule of self-defense: practice good situational awareness. If you have allowed a mugger to sneak up behind you and get within striking distance, your top-shelf gun may as well be a paperweight.

Criminals, whether robbers, would-be rapists or just vicious street toughs, always look for those who are not paying attention. Are you carrying armloads of groceries to your car? Are you forgetting to “keep your head on a swivel” — staying constantly aware of everyone in your immediate vicinity?

Are you preoccupied, talking on your smartphone as you walk? Or worse, texting? Interviews with muggers and rapists confirm that those are behaviors they actively look for in potential victims.

Predators have also developed simple but surprisingly effective techniques for “closing the distance” — asking you if you know the time or if you can give them directions, all the while edging closer to you. If this happens, you have every right to put your hand up and say something like, “Stop right there. I don’t know you.”

But use common sense. Obviously, if an elderly woman in a crowded food store asks the time, or where the post office is, the odds of her being a threat is virtually nil. But the same questions from several young males in a deserted parking lot, especially at night, is a different story.

So be constantly vigilant and aware, use good judgement and be ready to react if someone approaches you uninvited — especially if your “threat detector” starts bouncing into the red zone. It just makes sense; distance really is your friend.