Re: Being your own teacher
"becoming your own teacher" - well... at some point you conduct your own research into how things work.
The more you know, the more you realise you don't know. Instead of taking that as a reason to hang it up, your disconsolate yudansha friend can see it as a challenge to learn more.
I read of a judo practitioner from before my judo career who said "I take my worst technique and work on it until it's not my worst technique any more. Then I take my worst technique and work... (you get the picture)... Eventually the first technique makes its way back to the bottom of the pack for more training.
I seem to recall reading something about O-Sensei saying something like "I think I've figured out Ikkyo" when he was in his 60s or 70s or something like that...
Hang in there.