Good topic, and I especially appreciate the first quote. Lewis also covered humility a bit in The Screwtape Letters:
You must therefore conceal from the patient the true end of humility. Let him think of it not as self-forgetfulness but as a certain kind of opinion (namely, a low opinion) of his own talents and character. Some talents, I gather, he really has. Fix in his mind the idea that humility consists in trying to believe those talents to be less valuable than he believes them to be. No doubt they are in fact less valuable than he believes, but that is not the point.
I believed this for many years, and it’s still hard to get out of that way of thinking, that “being humble” means having low self-esteem. Tim Keller has a very short book called “The Freedom of Self-Forgetfulness” which is on my bedside table but I haven’t started it yet (as with many other things 
). I’m looking forward to it though – he tends to have very probing, succinct observations.