Although I teach a japanese style of jujitsu I would welcome advice from practitioners of other styles as well. At our school we typically focus on a kata curriculum in a fairly low stress environment. There isn't usually a lot of adrenaline pumping though students as they repeat a known set of moves. Regardless, there are students that seem to get so focused on what they're doing that they forget there's a human partner on the other end of the technique.
Even after years of training with some students I can't seem to shake them of the tendency to forget they're supposed to go slow and not rely on muscle to make a technique work. A simple leg sweep to the rear has resulted in a few students getting blasted into the mat on the backs of their heads. I've spoken to these students and they're very apologetic and I don't have any impression that they're just the macho type trying to show off; they do want to get more relaxed and controlled but can't seem to will their bodies to do it.
I'm wary of having these students practice anything other than kata because I suspect adding the adrenaline of a sparring situation would be dangerous. I've had some limited success with an extended warm-up that makes them too tired to be tense, but this always seems a temporary fix. What are some things I can have them practice to help them learn to relax "under fire"?