I'm working on it.
The cheap answer is "mindfulness." You and your students need to know what you are actually doing and, more importantly, what you are not doing. Sparring is an okay way to work on timing, an excellent first step to teaching tactical awareness and sometimes intuition. It is not practicing self defense. That's not enough, either: for non-grappling systems it actually hurts your distancing (you either have to pull or you are wearing gloves that can displace the point of contact an inch or so, and an inch off in a fight can suck) can compromise your power generation (I'm a relatively small guy who doesn't train full contact- the last time I went somewhere and had to box I broke two ribs through armor while wearing sixteen ounce gloves- the guys who trained full contact weren't hitting that hard, because if they did, they run out of students. They were hitting light AND didn't know it AND thought they were hitting "right".)
So that's the first thing, know what you are doing and, more importantly, know what you aren't doing. Does any of this make any drill bad? Hardly. As long as you milk it for what is there, there aren't many bad drills. They just get dangerous when a student (or, gad, an instructor) believes that it is something it isn't.
Second, always know the flaw in the drill. Quoting myself: "In the end, a martial artist is training to kill, cripple or maim another human being. In any drill where the students are not regularly taken to the hospital, there is a safety flaw built in."
Judo starts from the very beginning with a very specific follow-through to the hip and shoulder throws. Students are taught that this follow-through increases control and sets up the uke for a quick arm-bar or osaekomi. The simple fact is that the four traditional follow-throughs either shattered the shoulder, snapped the neck, broke the tailbone or knocked the wind out. The judo follow through is taught as control, but was introduced for safety.
The pronated fist in karate is almost unheard of in the Okinawan systems. It was (according to one of the grand old men of shito-ryu) a Japanese innovation to make the strike safer- the Japanese were not willing to allow the number of training deaths that the Okinawans did. That one should be obvious to anyone who has paid attention to their own body while hitting a bag: pronating the fist shortens the arm, it makes the wrist much weaker, it forces an unnatural bend to get the two big knuckles in line with the radius and ulna (resulting in many strained wrists) it even crosses the radius and ulna. Everyone who has done this has felt it... but it was "the right way" and they made up a bucketful of myths about why it was the right way.
So, suggestion number two: always look for why your partner is not going to the emergency room. It's okay -critical- to have safety flaws. We need to recycle partners. But be mindful that it is a flaw and be sure to balance it with another drill that works to offset that flaw- if you've been playing pitty-pat sparring with a partner, take some time to unload on a heavy bag (and watch your feet and you will see that not only did you shortchange your power generation when sparring, but you stand much closer to a bag you want to unload on than a person you are playing with- which distance do you suppose is right?)
Corollary to suggestion number two: Don't practice the flaws! If you find that you are expected to put extra time or effort into perfecting the part of a technique that is designed to not hurt someone, walk away. Seriously. I would leave an instructor in a heartbeat who was wasting time like that.
Third, don't practice against imaginary attacks. We know a lot about how people really attack. We know about monkey dancing and how to avoid that. We know about predatory assault and how those are set up and executed. We know how domestics go bad and what an enraged person is likely to do with a kitchen knife. Most stuff works against the monkey dance, including walking away. Great- we got the skills for the one we can avoid. There is no one way an attack will happen, but I will go out on a limb and say that there are a few ways that they almost never happen: the slow-motion lunge from two feet out of range and the slow motion downward stab, both holding the arm in one place for long enough to do something to it. About ninety percent of all martial arts weapons defenses that I've seen are concentrated against attacks that I've never seen outside training (Not just martial arts, the one they taught at the academy was one of the worst).
Bad guys aren't stupid and they don't use weapons for an edge. They use the weapon to finish things. They attack with surprise, from very close with all the power and speed they can muster, preferably inhibiting your movement at the same time. If you honestly give the guy with the weapon permission to act like a real bad guy, you will lose. A lot. You probably won't find anything that works, but you will find a few things that work better and, strangely enough, you will find those things centered around fast, close, hard and surprise.
Discouraged? Don't be. You might not find answers training this way but you will become very familiar with the question, and that is a huge advantage. The danger or temptation here is to just slip back into the old ways. Go ahead and drink the grape kool-aide and have your uke be stupid and slow and obvious, because that works, baby.
When you let your bad guys be bad guys, it's a whole new world, and your skills build at an amazing rate.
Last (for now)- break patterns and freeze. This one applies especially to grapplers, but it also works for anyone and I even do it in restaurants: freeze the drill, stop, and think- If I had to take this guy out completely, right now, how would I do it? In almost any situation if you have any skill at all there is a pretty reliable finishing option- C-1, eardrum, philtrum, throat, carotid triangle, jaw hinge, peritoneal nerve, knee, ankle...
It's a good mindset game, but the real question, once you realize that one of these is almost always right there, is why you weren't already doing it. Why is this a break from your pattern? What pattern were you in? Playing a game? Locked in a rut?