Lewis is not saying we have to "learn to love ourselves." He accepts that we do automatically. He's explaining what self-love consists of, and what it consists of is good will toward oneself. One keeps on having good will toward oneself no matter what one does.
Some people experience keen self-loathing, sometimes terminally so.
Self-hate is self-love in disguise because you wouldn't hate yourself for your failures if you didn't love yourself so much you couldn't stand having the flaws that cause the self-hate.
Humility, true humility, as opposed to self-love /self-hate, would accept all the flaws and the failures without getting all depressed about them. And in that attitude there may be a really healthy self-love.
I think you are bordering--nay, trespassing--on sophistry here. The Sophists were famous for being able to persuade you that black was white, only to then change your mind back the other way. :)
I think most people are stuck with themselves, not on themselves, and learn to live with their shortcomings.
I don't think people kill themselves out of self-love--they choose death to end intolerable pain, a quite different matter.
I don't love myself. I don't hate myself. I've come to terms with my strengths and weaknesses, and I accept the fact that I've done some very good things and some terrible things. I know I am neither the best of persons nor the worst. I try to do better.
I find the injunction to love thyself an odd idea if taken without instructive irony: to me, love places an Other above the self.
Self-love is a masturbatory, contradictory notion. A strong will to survive--even at the expense of self-delusion--is not the same as self-love.
I don't believe Robin loves himself, either. I think he takes good care of himself, by his own lights, but that, too, is another matter.