Avoid petty fights.
If you can walk away, do so. There's plenty of scum in this world who just want to drag you down to into the mud to hurl feces at you.
If someone is legitimately terrorizing you or someone you know then, run away and, call the cops. It always helps to have the jury on your side if anything real goes down.
The only situation where I'd justify fighting is if you fear for your life or the life of another innocent person and there's no 'golden bridge' to escape or way to diffuse the situation. At that point to me it's not fighting anymore, it's neutralizing, and I'd use any tools at my disposal to take care of the threat up to and (very unfortunate) including lethal force. no respect and no mercy.
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I've been in a couple fights back in highschool. Both were situations where trouble came looking for me, I was just minding my own business and I guess some reject was trying to show off to his little piglets how tough he was. I suppose I was passive aggressive, acted arrogant when I was approached.
I was in the wrong place at the wrong time. They were dirty fights, I guess I don't fight fair(blood and broken teeth). I was suspended for a little while for both, and now that I look back on it it was pretty embarrassing to get dragged down to that level by some deadbeats. I could have walked or ran away but I didn't, and now I wish I did.
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Save that aggression for when it really counts. If some deadbeat wants to fight you, just think to yourself what it's over and whether you care that much. Look down on petty fights and see them for what they are ... pathetic.
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I'd also recommend doing some form of martial arts so you aren't clueless in an unarmed self-defense scenario. Would carry a knife too, and learn how to use it. Also if you're legally allowed in your area and are inclined to take control of your life and future, would get a concealed carry permit and learn how to use the firearm. Again self-defense isn't cute or noble. you do what you have to do to get the deadbeat away from you, using however much force you need to.
getting in a fight because some monkey hurled his verbal feces at you is just embarrassing.