Heinlein was absolutely right about one thing: people are significantly more cautious about their own actions when they know they may have to pay a high price as a consequence. Exactly the same rule applies to criminals… particularly to criminals.
Any criminal worth his salt will try to obtain maximum benefit with the least risk possible for every opportunity he seeks to engage in. The risks involved in committing a crime can range from getting a free ride in the backseat of a police car to significantly more serious consequences such as spending many years behind bars, or even worse, ending up in a one-size-fits-all black body bag.
Therefore, there is an additional, yet equally important advantage of being in a position of defending oneself via an armed response, which consists of the demonstration of force. This demonstration of force will serve as a clear and powerful disincentive to any would-be-attacker by showing them that there is an imminent high risk in engaging or continuing to pursue a particular target for his criminal purposes.
A common response when it comes to armed self defense that I’ve heard over and over (not that I believe it to be consciously true) is, “No, I can’t have a gun at home. I would never be capable of shooting anyone, not even a criminal breaking into my home.” Yet, this kind of thinking fails to take into account the significant amount of incidents in which a crime was prevented because the victim was able to stop the criminal by the mere show of force, without actually having to shoot the attacker.
However, this is not in any way, shape or form a statement advocating the use of a handgun or any kind of weapon for intimidating purposes, as this is a truly dangerous approach to self-defense. Anyone who has decided to resort to an armed response must be mentally committed to use the weapon until the threat is neutralized. Nonetheless, there is a great amount of evidence demonstrating that a victim was able to stop the commission of a crime by using a firearm without actually having to shoot the attacker.
According to a study, citizens use firearms approximately 2.5 million times every single year in self-defense. In over 90% of these cases, citizens stopped the criminal by simply showing their firearm or firing a warning shot to intimidate the attacker. 
The thoughts going through the mind of a would-be robber, rapist or killer of facing his own demise via “lead intoxication”, specifically 9mm lead rounds to the forehead, is perhaps the best thing that can happen to the person holding the weapon (and to a certain degree, the criminal as well, considering the other less favorable options).
According to a study made by the US Department of Justice, three out of five felons polled indicated that criminals refused to engage a victim whom they knew was armed. The same study indicated that 74% of felons polled showed that one of the reasons why burglars avoid breaking into houses when people are at home is because they are afraid of being shot during the burglary.
Additionally, contrary to the typical, tired, stereotype of armed citizens portrayed by the mainstream media or gun control advocates, with very few exceptions, no law abiding citizen wants to shoot a criminal in self-defense unless they absolutely and positively have to do so. Besides any possible psychological, emotional and religious apprehensions people may experience about taking a human life, fear of prosecution, trial by media, and other repercussions are tangible fears running through the mind of every law abiding, decent, working person who has to confront a criminal.
The thought of having one’s face plastered in a mug shot wearing an unflattering and oversized orange jumpsuit, having some random opportunist politician hugging the crying family of your attacker on national television, and perhaps having to sell your left kidney just to pay legal bills are sufficiently powerful psychological deterrents for anyone to unnecessarily escalate an attempted crime into a shooting.
Therefore, being able to de-escalate a lethal confrontation while eliminating the threat by sheer intimidation of a criminal is a successful application of self-defense and a win-win situation for all parties involved. The criminal doesn’t end up getting shot and the law abiding citizen doesn’t have to worry about having an army of unfriendly attorneys, journalists and a jury second guess a split second decision.
The ability to neutralize your attacker without being forced to get involved in an actual confrontation with him is such an important advantage that it was acknowledged more than two thousand years ago by Sun Tzu as one of the most important principles in the “Art of War”. It instructs, “Therefore the skillful leader subdues the enemy’s troops without any fighting”. Considering that the advice of the world’s most respected war tactician in history has been applied to major armed conflicts around the world for centuries, there is true wisdom in his advice that we can all apply in a self-defense situation.