It is. I did somewhere around ~10mins or something in my first try. Which I was told is very high for a first attempt. But it is indeed difficult. Like @dymk said, you work your way up.

Also, a lot of folks think it's easy to do. Until you try it, that is.

I also remember reading somewhere around the lines of handling the chaos in your-self. Or controlling the chaos within yourself.

And always thought this exercise showed what that is about. (Sorry, forgot the expression. Been a while. It's definitely more nicely put than the above.)