If the old fairytale ending “They lived happily ever after” is taken to mean “They felt for the next fifty years exactly as they felt the day before they were married,” then it says what probably never was nor ever could be true, and would be highly undesirable if it were. Who could bear to live in that excitement for even five years? What would become of your work, your appetite, your sleep, your friendships? But, of course, ceasing to be “in love” need not mean ceasing to love. Love in this second sense—love as distinct from “being in love” is not merely a feeling.
They can have this love for each other even at those moments when they do not like each other; as you love yourself even when you do not like yourself. They can retain this love even when each would easily, if they allowed themselves, be “in love” with someone else. “Being in love” first moved them to promise fidelity: this quieter love enables them to keep the promise. It is on this love that the engine of marriage is run: being in love was the explosion that started it.
People get from books the idea that if you have married the right person you may expect to go on “being in love” forever. As a result, when they find they are not, they think this proves they have made a mistake and are entitled to a change—not realising that, when they have changed, the glamour will presently go out of the new love just as it went out of the old one. In this department of life, as in every other, thrills come at the beginning and do not last. The sort of thrill a boy has at the first idea of flying will not go on when he has joined the R.A.F. and is really learning to fly. The thrill you feel on first seeing some delightful place dies away when you really go to live there.
This is, I think, one little part of what Christ meant by saying that a thing will not really live unless it first dies. It is simply no good trying to keep any thrill: that is the very worst thing you can do. Let the thrill go—let it die away—go on through that period of death into the quieter interest and happiness that follow —and you will find you are living in a world of new thrills all the time. But if you decide to make thrills your regular diet and try to prolong them artificially, they will all get weaker and weaker, and fewer and fewer, and you will be a bored, disillusioned old man for the rest of your life.
—C.S. Lewis, Mere Christianity