those who can ...

...... frequently can't teach.
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It's the other side of the the "those who can, do; those who can't, teach" equation -- the people who best know how to do something, often don't know how to teach others to do it, simply because it comes so easily and instinctively to them that they don't know how to break it down into simple steps that others less skilled than them can follow. It's the rare teacher who is also among the best at what he/she does.
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On the other hand ...
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i have this theory that "those who can", and who want to shape and influence and mould, often make good mentors. Which is different from being a teacher. The way i see it, mentors are people who guide you while you're making your way. They've been on the journey that you're on, and they're further ahead than you, and they're helping you to find your way yourself. They don't always teach; sometimes (mostly?) they give advice, and act as a sounding board. And when they do teach, it's not the basics that they're teaching, because they work with 'mentees' who have talent and potential, who just need someone to help polish that potential and turn it into something shiny and new.
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