I like a double-impact. Joseph Joubert remarked, "To teach is to learn twice!" In school I was happy enough to learn it once! But there is wisdom in this thought... learning it yourself to the degree that you can share your learning and enjoy the miracle of watching the person you tell or show that second time around. It's a blessing!
I remember it was said of Lincoln that he acquired a straightforward use and style of the English language as he taught himself to read, think, and write. In that Victorian era of flowery prose, his words stood out by speaking to the essence of the issue-- and still do! The first success was the clarity it brought to his own mind; the second was the clarity it brought to all people-- in all ages-- who have read his words.
To think clearly is to learn for yourself; to write it down is to leave that imprint for another to follow. And to bless them.