Be sure there is something inside you which, unless it is altered, will put it out of God's power to prevent your being eternally miserable. While that something remains there can be no Heaven for you, just as there can be no sweet smells for a man with a cold in the nose, and no music for a man who is deaf. It's not a question of God 'sending' us to Hell. In each of us there is something growing up which will of itself be Hell unless it is nipped in the bud. (God in the Dock, pp. 154-155)
Some people say, "You are what you eat." But far truer than that is, "You become like what you worship." We were made in the image of God, and our destiny is to be more perfectly conformed to the true image, Christ. This is why idolatry is so dangerous. When we worship the living God, we become more greatly conformed to the ultimate source of all Life, all Love, and all Truth. And so, when we set aside all our defenses and really let God transform us as we worship him, we become increasingly like that source. But when we worship what isn't God, when we 'exchange the truth of God for a lie, and worship and serve created things rather than the Creator' (cf. Romans 1:25), what we're being conformed to is at best a shadow, not the real thing. If I devote myself to something that's at best a copy, I'll always have that thing standing as an obstacle between myself and the reality. And if I devote myself to what's imperfect, how on earth can I ever be conformed to the image of perfection; how can I ever be perfect as my Father in heaven is perfect (Matthew 5:48)? But the thing is, we all commit a sort of idolatry: suitheism, the elevation of ourselves as our own little gods. Because every act of pride, every sin, is in effect a declaration that God is not the true lawmaker and that we know better how to run our lives; and that act of declaring ourselves the ultimate authorities on ourselves is idolatrous. And when we fall into the trap of worship of self, we get stuck in an infinitely vicious recursive loop. And if we're meant to be productive, then--figuratively speaking--that sort of self-worship strikes me as the ultimate in spiritual incest, if you'll pardon the somewhat disturbing imagery.
God doesn't lay down the law arbitrarily, as though it's fun to do so or anything like that; his commandments are a glimpse at the operating manual for our nature, the operating manual that comes with being made in his image. They're a guide to true human flourishing, to entering into the realm directed and guided and enlivened and illuminated by his Spirit. So when part of that operating manual says to be oriented out from ourselves and towards him, I don't think that's because of any neediness on his part--far from it! It's because it's not only the right thing to do, but it also happens to be ultimately good for us.
We're flawed. If you don't think you are, then the only advice I can give you is to do some serious reading of Paul's ethical exhortations and then to find somewhere quiet to do a whole lot of serious introspection. The best cure for delusions of perfection is a thorough self-examination in light of what we're supposed to be. For those of us with a more realistic image of ourselves, and especially those of us who can grasp that this problem isn't just a trifling matter, I think it's easier to see Lewis' point. Apart from Christ, I have some flaw deep inside of me that's killing me; it's like a fatal poison or terminal illness. It's like chronic pain for the soul, a metaphor I can definitely relate to. And I think that Lewis may very well be right: that flaw, that pride - because some form of pride is, I think, the ultimate ground of every sin - is something that will never let us be at peace until it's dealt with. In the life we're called to live, there's no room for pride or pretensions of autonomy; we have to concede that we haven't been put at the top of the pecking order, and in fact that we didn't pick our station in the great chain of being at all. We also have to put aside all our silly notions of second-guessing God - and, let's be honest, we all do it on a pretty regular basis. Unless we do all that, we'll never be fit to live the true life, the life we're meant to live.
So like Lewis said, that flaw, left unchecked, will keep on being magnified through our self-worship; just like a proper fraction multiplied by itself keeps getting smaller and smaller, so too does our deficiency get magnified every time we worship ourselves. And left unchecked, that shrivelling up will be hell. I'm enchanted by the way Lewis portrays hell in The Great Divorce, as the uttermost in smallness, where what was once a magnificent human being has, because of its orientation inward, just collapsed in on itself and diminished. And if God is the ground of all being and the ultimate source of existence, and if our sin and imperfection is a diminishment of being - again I borrow from Thomas Aquinas - then that continual process will bring us to asymptotically approach nothingness, just as even the continual multiplication of 0.99999 will eventually get closer and closer and closer to zero.
Perhaps it was Lewis who somewhere also said that to a reprobate man (or woman), the atmosphere of heaven would be more hell than hell itself; it's not the right polarity for him (or her), and it's simply too rich and too solid, the way Lewis portrayed the heavenly life in The Great Divorce. Just as some people can't handle natural food or natural air, and so can only stomach weaker things, so none of us, because of our sinfulness, are able of ourselves to handle the life we were meant to have, and can only be acclimatized properly through grace; like Lewis' fictional tourists from hell to heaven, so if a sinner were thrust into the sort of life we'll live in God's presence someday, it would be unbearably heavy and oppressive; it would be like putting a toddler in the middle of an NFL game. If we - spiritually speaking - purposefully infantilize ourselves and spurn the grace and love of God, we'll never be hardy enough for what we were made to do and be; we will forever be wasting away. We need to put off that weakness, extirpate that cancerous seed of hell within ourselves - or, to put it more truly, to throw down our shields and cooperate as Christ treats it throughout our lives so that it won't dominate our futures in the world to come. It's just like Lewis ended that essay: "The matter is serious: let us put ourselves in His hands at once--this very day, this hour" (God in the Dock, p. 155).