Only once since I'm a very mellow and peaceful person 99% of the time... and I can't really remember it, I can remember what led up to it, took my baby sister (ok she's 20 now but she will always be my baby sister) out clubbing on her 18th birthday, playing designated driver for her and a few of her friends, to hopefully put my reaction in a bit more context I love my sister to death, she means the world to me!
Anyway while in the club I was keeping an eye on her from the bar as there were the usual dicks out and about at clubs on weekends looking to get laid and generally being douches and this being my sisters first night out she might not have been aware of the sorts of people who are out there.
Now there was one guy who was hounding her and I had a really bad feeling, then when he grabbed her and tried to kiss her I got up and started walking over, when she shoved him away and yelled at him, his pride must have been bruised because he got angry and backhanded her... that made somehing snap in my and I cant quite remember what happened next, I remember running to her... but I kind of had a "black out" moment and came back to my right mind being restrained on the floor by 2 bouncers because apparently no matter what anyone said I wouldn't stop and that right there terrifies me
Since then I just try not to do anything that will get me into anything like that situation again, haven't been clubbing in years, never go anywhere near alcohol outside of the house, dont leave the house after 9pm on weekends if I can help it
I don't regret it howevever, being there for my sister, not for a second!