When you have experience in something, you are always looking forward to do it since you're so good at it, in other words, you are always <em>KEEN</em> to do the activity you are good at, you are basically a pro at it.
Explanation:
A keen teacher and 'experience' are pretty relatable, the teacher is obviously very keen to teach something they have experience in, and experience is like for example a math teacher, who has lots of experience in math.
