In general, if you have to use violence to defend yourself, you may have to justify that in court. If you use potentially or actually lethal force, the chances of having to justify it in court go up exponentially.
One of your primary defenses will be how you were trained, what you learned during your education process, and how your defensive mindset was formed. As part of that, it helps to document your training through class notes (taking them yourself if necessary), video clips of the instructor (often found on YouTube), recordings, etc. You can also introduce as evidence material from others that reinforces and supports your defensive mindset.
I'd like to show you one such piece of material this morning, particularly because Antifa, the progressive far-left-wing movement behind much of the anti-Trump and anti-conservative unrest of recent months, was advertising credit-card-sized concealed knives on its Web site. These things may be tiny, relatively speaking, but they can do an awful lot of damage - potentially disabling damage, if not inflicting permanent injury such as the loss of an eye or a severed nerve - in the hands of someone who knows how to use one. The odds are increasing that people like us may run into one of these demonstrations - so it behooves us to be prepared to counter such violence, in defense of ourselves and our loved ones.
Here's what even a very small knife can do to a human being. I recommend watching the video in full-screen mode.
Remember that video. Bookmark it and/or save a copy for future reference. Remember Antifa's attempts to sell knives of similar size to its members, and their open discussion about the need to arm and train themselves. Remember it if you run into them while about your lawful business . . . and keep them out of knife range, by whatever means may be necessary (and, of course, legal - that goes without saying). If you ever have to justify that decision and/or your actions, play back that video in court, point out Antifa's discussions and its efforts to sell knives to its members, and make it clear that you considered yourself in imminent danger of suffering similar injuries unless you stopped them. It's a compelling argument.