Re: Becoming an instructor
I think it's a mistake to believe that the instructor should never screw up.
My original sensei was a shihan, but he said that he didn't go for 100% perfection. He said he was happy if his technique worked 60% of the time. I think he was being overly modest! I believe the point he was trying to make is exactly what other posters on this thread are saying: if you are still progressing it means that you are occasionally going to do something different from usual (as an experiment) that doesn't necessarily work. Everyone in the dojo knew that he was way further along than his students and was a truly excellent teacher.
Aikido is hard. It's okay to screw up, even if you are teaching. Fear is paralyzing and cannot have a positive effect. Additionally, humility can be powerful.