Older sister now runs our business, a gym, after parents passed away. She's 21, I'm 19.
She's a former junior national kickboxing champion and a 2dan karate black belt. I'm not an athlete, I simply workout under her guidance, she keeps me fit and healthy, we prep meals together. In all, we're cool.

I got annoyed yesterday after she passed a comment about me. We had a heated argument after that I challenged her to a fight. Never before have I fought with her physically, add to that, never before did I want to hit a girl so badly as yesterday.

I got a taste of her kickboxing skills yesterday. I ended up with a black eye, broken nose, and 2 broken front teeth and was saying sorry multiple times, begging her to stop several times, before she finally stopped kicking me.
She quickly calmed down after she saw i was hurt badly and held an icepack to my face for about an hour or so then took me to ER, and later apologized profusely, and spent the day watching movies with me.

In this case it was my own sister, so no one else will know I got beat up by a girl. But in my mind, I know now that I can't fight if my life depended on it. She's promised to train me in boxing and judo, but I'm feeling a bit emasculated. I love my sister don't get me wrong, she's the only family and support I have.
Any advice?