Re: The Sixth Sense
The first time it was me up in front leading, I realized that the reflective glass over the Ki symbol in the tokonoma explained part of sensei's uncanny ability to know what was going on behind her!
But there really is a learnable skill here. Having children, or just teaching children, teaches this--after many bad experiences you get a strong intuition for where they are and what they are up to all the time. ("Why is it so quiet? Uh-oh....") I think that of all the training my dojo offers, being assistant instructor for the younger kids' class is the most powerful for working on overall awareness and sensitivity.
Working blindfold is very, very cool; I haven't been able to do it often enough to get any proficiency, but it should really help. Grabs are enough, you don't have to risk strikes.
If you are worried about developing paranoia, ask your friends to challenge you at specific "permitted"
times and places, not all the time and everywhere. It's safer for them, too....