For, make no mistake: if you are really going to try to meet all the demands made on the natural self, it will not have enough left over to live on. The more you obey your conscience, the more your conscience will demand of you. And your natural self, which is thus being starved and hampered and worried at every turn, will get angrier and angrier. In the end, you will either give up trying to be good, or else become one of those people who, as they say, "live for others" but always in a discontented, grumbling way--always wondering why the others do not notice it more and always making a martyr of yourself. And once you have become that you will be a far greater pest to anyone who has to live with you than you would have been if you had remained frankly selfish.
--C.S. Lewis, Mere Christianity
Crossposted at The Catholic Breadbox