The super risk takers, the kind of people who are willing to walk into a burning house or enter a combat fire fight, at first appear incredibly reckless, possibly suicidal. Its normal to think that because their behavior dramatically differs from how normal people perceive and interact with the world.
Instead those people simply lack a certain form of emotionally regulated fear as a stress response. That difference can occur from extensive training and conditioning, but in more extreme yet casual cases its something a person is born with. Their bodies still tense up, they still produce adrenaline, and their pulse still shoots up like everybody else so they are reacting to stress with a stress response like normal people. The difference is that their inhibition due to that fear is more rapidly eliminated by a neurotransmitter. That allows two things that normal people don't realize occurs:
1) The high risk behavior is primarily a means of learning to interface with the world in a new way.
2) The resulting high risk action is often the result of a rational risk calculation in a snap moment, similar but opposite of panic.
The edge, if any, comes from proving something or eliminating a consequence other people aren't willing to attempt. The consequence though, is that even if such people are able to realize and prove this edge most people will not be willing to accept it.