There's an old rule when it comes to self defense. If you can leave your house, you better be ready to fight. If you're serious about your self defense you should always train regularly. Training when your injured is even more important than training when your healthy.
Practicing healthy is easy, you feel good, you're confident and aware when all systems are go. But when you're injured, the opposite is true. You're confidence is down, you're distracted and focused on your injury or your illness. This presents a serious problem because when you're injured the likely hood of your being attacked goes up exponentially. A criminal will target you because you are impaired, for this reason alone you must prepare yourself.
The first and easiest solution of course is weapons and technology. Arming yourself and training with your weapon(s) of choice while you're injured is the first thing you need to do. It's a whole new ball game working with one arm or one leg and you have to know how to make the adjustments in order to survive. Using and "equalizer" of sorts will allow you to make up the difference between being healthy and being injured.
Practice hurt. The same holds true for your empty hand techniques. You must know your real capabilities. Taking stock of your abilities can only be accomplished through actual training. Adrenalin will only last so long (30 seconds) and get you so far depending on your type of impairment. When you train you will discover what you can still do and what you should avoid at all costs.
Set the example for your students.
As an instructor you feel the compulsion to set the example by doing the best and being the best at all times. Well, if you're human, this is not always going to be the case and you're students know this. When you work with and injury it will serve to inspire your students. This will set the example and will help elevate their training as well as your own. When you over come obstacles you are truly being the best and setting the goal standard.
However, as an instructor, it's your responsibility to protect your students. Make sure they're not causing further damage to themselves. It's important to know who is hurt and watch them at all times. Protecting them from themselves will be your hardest job.
The same goes for you as well. Work with in your capabilities and give yourself a chance to heal, because if you push yourself too hard and too fast, a simple injury turns into a chronic problem. Don't let pride and ego cloud your judgment (I think this is the hardest thing for all of us to do).