How do they practice this sort of thing without killing themselves?

Not exactly a new video, but I still watch it from time to time and wonder how in the hell you become insane enough to do stuff like this. 
 
https://youtu.be/x76VEPXYaI0
 

Insane? Yeah! That course looked difficult to navigate, I was waiting for him to hit a bystander. Ahh heck that course looked so treacherous I'd have trouble just walking along it without sliding off the edge and into the abyss!

There's an idiot born every 10 seconds....  LOL

It's not the fall, it's the sudden stops that hurt. 

The skills required to walk a tightrope one foot off the ground are the same skills required to do it at 100 feet up. The confidence the performer has in those skills, and his ability to ignore the consequences of failure differ. Two basic types of people can manage the mind trick. There are people who simply do not have the fear response we consider normal, and there are people who get a near orgasmic reaction to fear, which has the quality of an addiction. A "normal" person can master the same kind of mind trick with practice and focused attention--but why would he?

I've seen a lot of stupid things in my life. Now I've seen one more. Yeah, I see the skill but the risk is not worth it unless there is some sort of safety that the video does not show. He went through some scrub near the end of the track and there were a lot of places where there were two trails to choose from. Maybe it isn't as dangerous as it looks. What do I know.
Julien

sharke
Not exactly a new video, but I still watch it from time to time and wonder how in the hell you become insane enough to do stuff like this. 

I'm with you on that Sharke.  Almost hard to watch, but I can't help not watch it. Fascinating video.
 
I guess I have to accept the fact that I am just one of the wimpy ones that leave these adrenaline rushes to the 'other' guy.

sharke
I don't know, I was fond of bridge climbing when I was young. We would clamber all over the beams and ledges of railway bridges, "tightrope walk" over supporting beams in high winds, that sort of thing. And what's more, we'd do it blind drunk as well. I guess I must have been 16, 17 - and at that age, it doesn't occur to you for one minute that you might die. Perhaps that's what kept us from falling, lol. But looking back I can't believe how stupid we were, and I get the willies just thinking about how close we were to being killed. You grow up.

I think the use of the word WE in that reminiscence goes a long way to explain the why behind a "normal" person taking risk for risk's sake. How often did you go off by yourself to walk across girders? The desire to prove your courage to your peers goes back earlier than dueling for honor or even counting coup. Peer pressure is a big factor in the ability of the armies of the world to take ordinary young men and, in a few short weeks, turn them into berserkers willing to charge into machine gun fire.
 
When I followed the link to the video I had to wait a minute before I could bypass the GoPro commercial. One factor in the current enthusiasm for extreme risks (weightlifting a clean&jerk of 263 kg or ultramarathons of 100 miles under 12 hours are extreme sports), is the ability to display your daring to an infinitely large virtual peer group via video captured on your buddy's cell phone or your own body mounted camera. I suspect the GoPro has probably put more kids into wheelchairs than ski jumping ever did before it became fashionable to see how many loops you could do instead of how far you could travel in the air. On the up side, the ability of death scene investigators to recover data from those tough little cameras has probably saved thousands of hours of speculative testimony in front of incredulous coroner's juries.

I saw a video on Liveleak yesterday of a young man in Russia falling to his death while walking across a crane...no doubt he was probably filming himself doing it....