Who doesn't know teaches, and who knows does it!
I don't know if it's the right translation (or if my English is good enough...), but here in Italy we use to say that about teachers and workers.
Considering that I work as a trainer for the 10% of my time and as a consultant/developer for the other 90%, I'm thinking about that...
As a trainer I think that I've to learn a lot (and I really learn a lot from my students), but as a consultant/developer I think that perhaps I've already learned too much!!!
What do you think?