I never felt nervous or paralyzed or stop breathing. I didn't really feel anything except maybe a little anger until it was over. I never felt the situation get out of control. I would have been emotional if I had to shoot him, but that would have been after everything was over.
To chase some one, when you have a gun, and they have a knife, is reasonably stress free.
You are most likely not a scardy cat, which makes the difference. As you say, it would have been a whole different set of problems, if you had shot him.
Some one who, on his own, is waiting to ambush who ever, in the open, has some guts also, and in this case was not stupid.