"The ordinary idea which we all have before becoming Christians is this. We take as a starting point our ordinary self with its various desires and interests. We then admit that something else--call it 'morality' or 'decent behavior', or 'the good of society'-- has claims on this self: claims which interfere with its own desires. What we mean by 'being good' is giving into those claims. Some of the things the ordinary self wanted to do turn out to be what we call 'wrong': well, we must give them up. [...] But we are hoping all the time that when all the demands have been met, the poor natural self will still have some chance, to get on with its own life and do what it likes. [...]
The Christian way is different: harder, and easier. Christ says, 'Give me All. I don't want so much of your time and so much of your money and so much of your work: I want You. I have not come to torment your natural self, but to kill it. No half-measures are any good. I don't want to cut off a branch here and a branch there, I want to have the whole tree cut down. [...] Hand over the whole natural self, all the desires which you think innocent as well as the ones you think wicked--the whole outfit. I will give you a new self instead. In fact, I will give you Myself: my own will shall become yours. [...]
The terrible thing, the almost impossible thing, is to hand over your whole self--all your wishes and precautions--to Christ. But it is far easier than what we are all trying to do instead. For what we are trying to do is remain what we call 'ourselves', to keep personal happiness as our great aim in life, and yet at the same time be good. We are all trying to let our mind and heart go their own way--centered on money or pleasure or ambition--and hoping, in spite of this, to behave honestly and chastely and humbly. And that is exactly what Christ warned us you could not do. And He said, a thistle cannot produce figs. [...]
That is why the real problem of the Christian life comes where people do not usually look for it. It comes the very moment you wake up each morning. All your wishes and hopes for the day rush at you like wild animals. And the first job each morning consists simply in shoving them all back; in listening to that other voice, taking that other point of view, letting that other larger, stronger, quieter life come flowing in. And so on, all day. Standing back from all your natural fussings and frettings; coming in out of the wind.
We can only do this for moments at first. But from those moments the new sort of life will be spreading through our system: because now we are letting Him work at the right part of us. It is the difference between paint, which is merely laid on the surface, and a dye or stain which soaks right through. He never talked vaugue, idealistic gas. When He said, 'Be perfect,' He meant it. He meant that we must go in for the full treatment. It is hard; but the sort of compromise we are all hankering after is harder--in fact, it is impossible. It may be hard for an egg to turn into a bird: it would be a jolly sight harder for it to learn to fly while remaining an egg. We are like eggs at present. And you cannot go on indefinitely being just an ordinary, decent egg. We must be hatched or go bad." (195-200 Mere Christianity, C.S. Lewis)