can explain more on "sometimes the brain can choose not to register the pain"? how can that be done without drugs intervention?

argument being they are diverting their attention on survival and death instead of pain? Or it's very much on consciousness? Once i climbed over the fence and i fall down, realising that there's a slight pain on my hand, it's not that painful until i look at it and find out that a portion of my flesh is torn....it is a choice to condemn the feeling of pain? i do not think that we can actually do it if we are conscious and not distracted by any other things.

Come back to the suicidal, when he jumps, he's diverting his attention to his problems, as such, when he crashes the floor, that intense pain lasted for few mili second because it kills it immediately. However, in his case, he manage to survive another 6 hours before certified death....do you mean that he will not feel the pain within that 6 hours because he never survive through. If he does survive through, then, he will feel the pain. Should i conclude that?