I think most people can agree that the jungle is a dangerous place. Predators hunt while the other animals hide and keep their distance. Without a sense of awareness the prey usually winds up at the top of the menu. I also think that most people would agree that man is the most dangerous predator of all. The threat by man is not always apparent and for the most proficient predators among us, their threat is rarely discernible until it is too late. How long do you imagine the beasts of the jungle would last if they purposely covered their sense of hearing? So why do so many people--women in particular--use earbuds when they are jogging? In spite of the fact that every year women are attacked--and sometimes murdered--while jogging with headphones. You wouldn't walk through the jungle with earbuds on, so why, when you are walking/jogging among the most dangerous predators, would you do it in an urban landscape? Or for that matter, what about the woman who was hiking the Appalachian trail listening to music when a bear literally bowled her over as it ran across the trail. She never heard it coming. Why? Because she was listening to music. A good example of natural selection and she she is extremely lucky she did not wind up on the menu that day.
This brings us to situational awareness. While it is impossible (and mentally undesirable) to be in a high state of alertness all of the time, we can and should, ramp up awareness under certain circumstances. For everyone but perhaps for women in particular, this might be getting into your car or getting onto an elevator; walking on a dark street; entering/leaving a subway during off hours etc. No one should be asking for "a light" or "the time" and if they do, then like USMC General Mattis, you should be ready to execute the plan ("be polite and have a plan to kill everyone in the room").
Evolution has taught us that predators need to be close to do us harm and when someone approaches to ask for money/cigarette/whatever, they are assessing you. It could be to see what you will give them but it could also be for far worse. Consider in advance how you would handle that kind of situation and play it out in your mind's eye. Better to work out the details in advance rather than in the milliseconds as a violent encounter evolves.
The other part of the puzzle is to practice how to visit violence upon another human being. This will also take mental preparation and some dedication to physical practice, to learn how to defeat a sociopath by fighting like a sociopath.
This is true whether you are using a "tool" like a firearm or other weapon or simply your hands. Situational awareness + mental preparation + training. Its a great way to stay off of the evolutionary menu.