He thought the first step to acquire humility is to admit your pride; the pride that can move in very subtle ways to set you up to its control:

Teachers, in fact, often appeal to a boy’s Pride, or, as they call it, his self-respect, to make him behave decently: many a man has overcome cowardice, or lust, or ill-temper, by learning to think that they are beneath his dignity—that is, by Pride. The devil laughs. He is perfectly content to see you becoming chaste and brave and self-controlled provided, all the time, he is setting up in you the Dictatorship of Pride—just as he would be quite content to see your chilblains cured if he was allowed, in return, to give you cancer. For Pride is spiritual cancer: it eats up the very possibility of love, or contentment, or even common sense.
Mere Christianity, 1952

Here is what he said on Pride in relation to God:

We must not think Pride is something God forbids because He is offended at it, or that Humility is something He demands as due to His own dignity—as if God Himself was proud. He is not in the least worried about His dignity. The point is, He wants you to know Him: wants to give you Himself. And He and you are two things of such a kind that if you really get into any kind of touch with Him you will, in fact, be humble—delightedly humble, feeling the infinite relief of having for once got rid of all the silly nonsense about your own dignity which has made you restless and unhappy all your life. He is trying to make you humble in order to make this moment possible: trying to take off a lot of silly, ugly, fancy dress in which we have all got ourselves up and are strutting about like the little idiots we are. I wish I had got a bit further with humility myself: if I had, I could probably tell you more about the relief, the comfort, of taking the fancy-dress off—getting rid of the false self, with all its “look at me” and “Aren’t I a good boy?” and all its posing and posturing. To get even near it, even for a moment, is like a drink of cold water to a man in a desert.
Mere Christianity, 1952

Oh how many are we who fall in this trap; only the Lord can set us free from this:

How is it that people who are quite obviously eaten up with Pride can say they believe in God and appear to themselves very religious? I am afraid it means they are worshipping an imaginary God. They theoretically admit themselves to be nothing in the presence of this phantom God, but are really all the time imagining how He approves of them and thinks them far better than ordinary people:
 that is, they pay a pennyworth of imaginary humility to Him and get out of it a pound’s worth of Pride towards their fellow-men…
Mere Christianity, 1952