Why did it start? I am guessing two factions goading one another until one person snapped and started swinging.
I still get that old familiar adrenaline surge if it kicks off near me but you just have to suppress it and walk away. One punch, somebody falls, bangs their head and dies and you're on a manslaughter charge at the very least. Five to seven years inside, sometimes more if found guilty. Not to mention living with the fact you've taken someone's life.
Too much to lose and all for a bit of booze driven ego. There is almost zero chance of getting away with anything these days, as aside from all the CCTV and dash cam cameras around, as soon as a row starts everybody is whipping out their phones and filming it. That's then posted online. You're then fucked. Wait until they roll out facial recognition cameras you're even more fucked.
No, smell trouble? Get away quickly. If in a pub drink up and leave. The next day you'll wake up sober, in your own bed instead of a police cell and smile.