Just a quick note to help put things into perspective.
A lot of what we do in the dojo looks harmless enough, since we are in the safety of the school (our "laboratory for the world outside") surrounded by our training partners and under the supervision of our talented teachers.
On the street, however, what we learn can easily escalate and be lethal. My original teacher used to remark "killing them is easy, the trick is to keep them alive". I had always thought he was joking. The reality is, he was not.
For an untrained opponent, the elbows, knees, eye/throat gouges, and the like can cripple or kill without very much effort. Because the action is fast, before you know it you will have done permanent (or even lethal) harm to an attacker. Even in the best case, you may get arrested and/or sued in court. Most of the time it simply is not worth it.
My net message: Many things in life, once done, cannot be undone.
Make sure you think twice before you hit once.
Martial arts training is a like a life insurance policy: you get it hoping you will never need it. If you do need it, you are likely to need it pretty badly. Only use it when aboslutely necessary.
Let's all be careful. With great power comes great responsibility.