Sandman, thats how I began in the nhb scene. Before sanctioned MMA became popular(I was about 18), there was a lot of underground fighting going on in San Francisco. I figured "Hey, I've got ten years of training behind me, time to make some cash!" Thats when I met the reality of being hurt. The dojo is a kindergarden class compared to underground shit. The way it worked where I went is that once you lost, you really couldn't fight again for a while because no one will put anything on you. I won my first several fights and developed a name. Things were great until I got hit in the throat pretty hard. It shocked me pretty bad which allowed the other guy to take me out with a kick to the head. When I got up, I couldn't talk. It just wasn't possible for me to speak. I would try and say something and nothing would come out. It stayed that way for about 3.5 hours. Scared the crap out of me. Its happened a couple times since, but never that bad. I rather have my nose shattered by a 2x4 than get hit in the throat.
I saw a few guys get their legs taken out(as in folded laterally), bones broken, joints folded, and lots of blood. I'm glad that NHB has become popularized to some extent. Now fights can be regulated and overseen for the safety of the fighters. More than once I really thought guys were never going to get up. There was always fights breaking out outside the pit. It was kind of a bad scene.