Grasping at... what?

Health is a great blessing, but the moment you make health one of your main, direct objects you start becoming a crank and imagining there is something wrong with you. You are only likely to get health provided you want other things more - food, games, work, fun, open air. In the same way, we shall never save civilisation as long as civilisation is our main object. We must learn to want something else more.

Most of us find it very difficult to want "Heaven" at all - except in so far as "Heaven" means meeting again our friends who have died. One reason for this difficulty is that we have not been trained: our whole education tends to fix our minds on this world. Another reason is that when the real want for Heaven is present in us, we do not recognise it. Most people, if they had really learned to look into their own hearts, would know that they do want, and want acutely, something that cannot be had in this world. There are all sorts of things in this world that offer to give it to you, but they never quite keep their promise (...) There was something we grasped at, in that first moment of longing, which just fades away in the reality.

C.S. Lewis

Mere Christianity Chapter 10 (1952)