Sometimes you find yourself in a situation where you have to make a big decision very quickly. You don't have time to weigh everything up and figure out the best possible way to resolve the situation- you just have to make your decision, act on it, and deal with the consequences. But, while your decision was the best you could do at that time, it may not have been the best solution, because the best solution may not have occurred to you under the pressure of the moment. So, while you did what you had to do, there was still a failure on your part.
How often are violent situations truly unavoidable? Speaking as a person who's seen a lot of them, the answer is "very rarely." 90% of the time, both parties to the conflict were in some way at fault, even if one of them was much more at fault. For every truly random attack there are many cases of two people acting more or less like idiots, often with tragic consequences.
Phil, if you're discouraging people from second-guessing themselves, you have a point but you should be careful. In the moment, you sometimes have to act decisively, and you don't want to be paralyzed with doubt when it could get you or someone else killed. You're right about that. But if you've ever seen how horrible the aftermath of a fight can be, you'll know that the decision to use violence on another human being should *always* fill you with the greatest reluctance and regret, even if there are times when you just have to set that aside and take care of business.
-Chris Thompson