As cops, we spend a great deal of time on "What ifs?" We develop tactical training scenarios based on both our experiences and situations we anticipate may occur in our business.
Our tactical planning orientation often extends to our private lives, too. We think about the risks around us and what actions we might take based on the threats we might face.
I would not suggest that private citizens become as obsessed with risk assessment as us cops. However, we see too many examples of people putting themselves in peril without considering the consequences.
Just this week, a victim got sideswiped by a suspect's vehicle while she attempted to retrieve her purse after it was stolen out of her vehicle. Fortunately, she experienced only minor physical injuries. In similar cases, many victims have died while trying to recover property of relatively little value.
I am not going to make blanket statements about self defense or how to respond in all situations. I would simply recommend that you consider all of the applicable laws and all of the potential variables, particularly the value of what you are seeking to protect, before you choose to go on the offensive.
There are plenty of good Internet resources available about protecting yourself. We even offer self defense courses from time to time. Again, I do not think you need to go overboard as you consider your own plans of action and we always encourage people to simply be good witnesses.
Someone much smarter than me once said that you plan to fail when you fail to plan. Unfortunately, the stakes are usually higher in crime situations and failure could be fatal. Please be careful out there.