In the past few weeks I have taught some stronger lessons. A wise friend shared this poem with me. Whitman's question is for the learner. I now see that the teacher learns as well.
HAVE you learned lessons only of those who admired
you, and were tender with you, and stood aside
Have you not learned the great lessons of those who
rejected you, and braced themselves against
you? or who treated you with contempt, or
disputed the passage with you?
from Leaves of Grass by Walt Whitman (1867)