In his classic, Mere Christianity, C.S. Lewis talks about The Great Sin. Concerning this sin, he says, "the more we have it ourselves, the more we dislike it in others." What is this great, ultimate, most devastating of all sins? Pride, or self-conceit. Lewis goes on:

Pride leads to every other vice: it is the complete anti-God state of mind... Pride is essentially competitive... [It] gets no pleasure out of having something, only out of having more of it than the next man. We say that people are proud of being rich, or clever, or good looking, but they are not. They are proud of being richer, or cleverer, or better looking than others... It is the comparison that makes you proud... It is Pride which has been the chief cause of misery of every nation and every family since the world began...

How is it that pepople who are quite obviously eaten up with Pride can say they believe in God and appear to themselves very [spiritual]? 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...

We have a test. Whenever we find that our religious life is making us feel that we are good—above all, better than someone else—I think we may be sure that we are being acted on, not by God, but by the devil... It is a terrible thing that the worst of all vices can smuggle itself into the very centre of our [spiritual] life.

If you meet a really humble man... Probably all you will think about him is that he seemed a cheerful, intelligent chap who took a real interest in what you said to him. If you do dislike him it will be because you feel a little envious of anyone who seems to enjoy life so easily.

So what are we to do?  The first step, Lewis says, "is to realize that one is proud... If you think you are not conceited, it means you are very conceited indeed." The good news is that the gospel invites us to confess our prideful passion for self-glory, cast it upon the cross, and receive the gift-righteousness of Jesus as our real, genuine glory. Gospel faith is the only antidote for the disease. It fosters true humility and illuminates the wonder of God's grace. So let your great sin lead you to the great Savior!