I. First Crush

I was 15 years old and went to the cinema to see a French film called L’Effrontée, starring the French actress Charlotte Gainsbourg, who was 14 at the time. I fell in love across an hour and a half. I was beguiled by her intelligence, tomboy beauty, and by what I ­perceived to be her sensitivity, modesty, and mixture of practicality and idealism. Looking back on the crush today, I realize how in line it was with what I continue to like in a woman. My 15-year-old self was not ­especially different from the adult self in this respect.

I went through several weeks of intense pain around the thought of Charlotte Gainsbourg—chiefly because I knew both that she should be my girlfriend and also that she never would be. I was freed from the pain by my very wise aunt who told me that human nature isn’t so cruel: She creates multiple examples of the same type and that rather than idly pining for Ms. Gainsbourg long into the summer holidays, I should follow the genus to which she belonged. “Find someone like her, but not her” was the advice. This was very releasing—and set me free to pursue other intelligent, tomboyishly beautiful, sensitive, modest, practical, and idealistic girls—a pursuit that ­eventually ended me up, decades later, proposing to my now-wife, who (strangely enough) happens to be called Charlotte.

II. Crushes of the 20s

I look back at my 20s as a golden age of crushes. I was often single, and there are, of course, no greater romantics than those who don’t have anyone to be romantic with. I often developed crushes on planes and trains. Once on a train to Edinburgh, I was assigned a seat across from a young woman sucking her way through canned apple juice. As we shuttled northward, I feigned a concern for the scenery (parched fields, industrial debris), while remaining glued to the angel. Short brown hair, pale skin, blue-gray eyes, a set of freckles on the nose, a striped sailor top with a small but undeniable splash of what might have been lunch’s macaroni. After Manchester, Juliet took out a cookbook, The Food of the Middle East. Her notes were taken in curled, ­concentrated handwriting—so endearing.

How little it took to fall in love. Or at least to fall into the kind of heightened enthusiasm for another person that might be called love, but also sickness or illusion depending on temperament. By the time the train was past Newcastle, I had thought of marriage, a house in a cherry-tree-lined street, Sunday ­evenings where we would quietly digest the Middle Eastern something-or-other that she had made and I would, at long last and forever more and with infinite ­gratitude, feel that I had a place in the world.

Perhaps such moments punctuate the life of many single males, unfolding without any outward sign, in the presence of faces glimpsed on trains, the lunchtime sandwich line, or airport concourse. Pathetic no doubt, but vital to the later institution of the couple. Spouses should subsequently acknowledge the importance of the previous despair of their unattached companions, for it is the foundation of future loyalty and selflessness—a reason, perhaps, to be suspicious of the romantically successful types, whose reliable charms have left them unacquainted with the tragicomic process of aching for days for someone one was too shy to address and whom one allowed to step off at the next station, leaving behind her carton of apple juice and one’s elaborate plans for marriage.

III. Crushes Post-marriage

But of course, after marriage things get more serious, more dangerous, more hurtful, and more catastrophic. Our society allows any sort of crush, fantasy, sexual experiment, and debauchery to take place before marriage. But thereafter, we are meant to slip behind a veil of sexual respectability and domesticity that would have reassured even a Victorian moralist.

Do I still have crushes now, as a married person? I feel shy answering the question, which really means, I don’t want to hurt those I love with my honesty. But I would also say that the capacity to develop a crush speedily depends on a certain degree of faith or innocence about human nature—one’s own and that of others. To be able to fall in love so quickly, one has to believe that it’s relatively easy to make a relationship work, so long as two people are keen on and attracted to each other. One has to believe that a little surface kindness and intelligence and beauty are reliable signs of total goodness. One has to have faith that there aren’t too many secrets hiding behind a delightful surface.

All these things become harder to trust in after a while—and therefore the capacity to develop crushes takes a hit as well. When I now sit opposite someone perfect-looking on a train, the following thought process goes through my mind:

1. She’s wonderful.
2. We would lie in each other’s arms in a field of flowers.
3. But she’d have a hundred complex characteristics which would make a relationship with her, even her, rather challenging.
4. What’s more, as I’ve just remembered, I’m not perfect either. Indeed, I am a monster, both internally and externally. With a passing resemblance to the Elephant Man, I regularly hurt those I love out of insecurity and spite. I shouldn’t be let out of the house without a warning sign.
5. I should leave the beauty alone, undisturbed by the sickness that is me.
6. Still, isn’t she wonderful?
7. We should lie in each other’s arms in a field of flowers …

Alain de Botton is the author of On Love, How to Think More About Sex, and the forthcoming novel, Scenes From a Marriage (Pantheon, 2015).