Rand is already learning it. I have a feeling that the lesson has more to do with not needing to rely on or become super weapons to win a battle. Cadsuane herself learned this and used it against Semirhage - by realizing that Semirhage was a rather shallow and stupid human being, she broke her in little less than five minutes. The Ashaman and Rand have to learn that it is their humanity that will enable them to win the Last Battle. It is as simple as noting how similar to Elaida Rand had become, to the extent that was exceeding her in arrogance, hardness and brutality. Egwene and Aviendha learned this lesson regarding understanding in TGS - every indication is that Nynaeve will learn it soon, as well.

I, for one, was very happy that Rand destroyed the male access key.