Towards the end of Mere Christianity, C.S. Lewis, writes honestly about the reality that Christianity requires a transformation that is very difficult business: 

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 down. I don't want to drill the tooth, or crown it, or stop it, but to have it out. 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 trying to do instead. For what we are trying to do is to remain what we call 'ourselves', to keep personal happiness as our great aim in life, and yet at teh same time be 'good'. We are all trying to let our mind and heart go their own way – centred 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. As 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 it 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 day or stain which soaks right through. He never talked vague, 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 (197-198).