Here’s a usual scenario: a man enters a mixed martial arts facility and dedicates his time to the craft. Proficiency in both a competition and a street fight was his primary goal. He starts beating people up in the gym, and his confidence goes through the roof. 

He then gets into an altercation with a belligerent drunk outside a bar one night. Armed with what he thinks are enough weapons to get him through, he engages in a full-blown brawl.
 

He gets beaten up and sent to the hospital with a broken nose and jaw. He may also never walk again after repeated kicks to the spine. 

Martial arts techniques don’t turn you into Superman. The streets aren’t kind to anyone, and knowing specific skills doesn’t always mean you’ll get out uninjured.