The argument from desire of C.S. Lewis reminds me of the Platonic conception of the soul. Plato said that the human sought in the physical world ideal objects, things that don't physically exist, things such as justice, good, beauty, etc., but could not find them and only found their reflection, that is, just things or beautiful things, but never justice or beauty, and so on. But finally, and if detached by the virtue of material things, and stopped pursuing reflections, at death they would find the satisfaction of such desires.

On the other hand, you are right in saying that no one but yourself can find such an answer, and that is because, even if the most wise words come from the mouth of another person, we are the ones who ultimately interpret them, and only when we are really willing to know such an answer, we will realize that it has always been there and everywhere, because that thing in which we can't give up, necessarily we have always had it with us, at least that's what I believe, I may be wrong.

Excellent post. Regards!