How can violence and self-control co-exist? How do you know when you are crossing over the line and you are seeking revenge? When is it no longer self defense or the defense of another?
Often, the answer to this set of questions may not come until after the fact. You may not realize that you have crossed a line until after that line has been crossed. In this case, your only resolution may be an apology. If the other person was also wrong, this can be especially difficult on the pride.
How do you properly make use of violence and still maintain your self-control? Lots of practice. Most people cannot do this without training. The same is true of becoming angry and not losing your self control. In fact, in this discussion, I would say that self control is of paramount importance. This is why people react with such shock when they see cops unfairly beating someone. They are given the reponsibility of using violence for the general good of the people they protect. Cops are therefore expected to exercise more self control than average.
I would argue that the difference between revenge and defense is also one of motivation. If, in your heart, your thinking is along the lines of "I'm going to teach this little bugger a lesson he won't soon forget," then your motivation may well be wrong. I can't tell you this; only you know what's in your heart. Maybe he does need a lesson. Maybe you are the one to do the teaching. Levi and Simeon certainly were. However, you must take great care with such thinking and see that it does not lead you into pride.
Thinking such as "I'm worth more than this," may or may not be wrong. It is not pride to know your worth. Most sexually abused women do not have a proper sense of their own worth. The same is true of those who allow themselves to be bullied.
As an aside, if you believe that letting it happen while you harbour hateful thoughts in your heart is somehow turning the other cheek, you are mistaken. You may as well lash out in spiteful rage, because I hate to tell you this: you are still sinning. It's just a different type of sin.
But back to self worth and self defense.
Knowing your worth is knowing your place in the grand scheme of things. Recall the centurion who said to Jesus that he was in authority and he was under authority. This statement applies to all people in all stations of life. There are people who are, for lack of a better word, "better" than you, and those who are worse. This could be in terms of their looks, brains, possessions, class, physical strength, whatever. No one is ever in the bottom of the pile. You are always somewhere in the middle compared to someone else on any given issue. Not standing up for yourself in the face of bullying or sexual assault presupposes that you are worthless, and this is not true. If you were honestly worthless, God would not have created you in the first place. All life has value. When facing some tormenter, keep this fact at the forefront of your mind. It is both uplifting and humbling.