It is two o'clock in the morning, and you are awake again — the bedroom dim, the world outside reduced to a single distant car and the small mechanical noises of the heating — and the argument that you and your partner had at half past nine, over a small thing, over nothing very much really, over a tone of voice that did not even, on inspection, exist in the way you thought it did, is still running its course in your head. You are rehearsing, with forensic care, what you should have said. You are reviewing the case for the prosecution. You are, in a calmer corner of your mind, also noticing that you are doing all of this about a person you genuinely love, who is sleeping peacefully three feet away from you, and who will, in the morning, almost certainly hug you and offer to make the tea.

Why is love like this? Why is it, of all the human projects, the one most prone to producing two-in-the-morning anguish, internal monologues of fastidious grievance, occasional minor acts of unkindness one did not know one was capable of producing? It is because love, more than almost any other undertaking we attempt, asks us to manage the gap between two separate human beings — and human beings, on close inspection, are mad. Not pathologically mad, and not catastrophically mad; but mad in the ordinary, structural, almost geological sense — patched together from old wounds, from defensive habits, from inherited blind spots, from badly-learnt lessons, from half-finished griefs. We bring all of this, unannounced and largely unexamined, into our relationships, and then we are surprised that the relationships turn out to be difficult.

Have you, perhaps, been holding your partner to a standard of sanity you do not, in fact, hold for yourself? It is a quiet and very common cruelty. We are tender about our own contradictions — we know our moods are weather, we know our flaws are old wounds rather than character defects — and yet we watch our partner do something rather innocuous (leave the cupboard door open for the seventh consecutive day, say something clumsy at supper, withdraw at precisely the wrong moment) and we file the moment not as their old wound but as evidence about who they fundamentally and disappointingly are. The double standard is unkind. It is also exhausting to maintain. And it is, when one looks at it honestly, very probably wrong.

What if your partner is, much like you, a flawed human being doing their best, on top of an accumulated weight of their own which you cannot see? This is, I think, the great compassionate insight available to people in long relationships — and one of the slowest insights to actually land. The mind, in the heat of irritation, would very much like the other person to be the source of the difficulty. The mind does not, on the whole, wish to admit that the other person is, broadly, like you — uneven, tired, occasionally unaccountable. The mind would, all things being equal, rather prefer to have a villain; a villain is so much easier than a fellow human being. Have you, on your worse evenings, made a villain of your partner? And on better evenings, recognised them again as a person?

This is the daily inner work of love — and it is not, please understand, the grand gesture, and it is not the romantic peak, and it is not anything one might recognise from films. It is the quiet daily insistence, against the part of you that wants to make them the problem, that they are, in fact, a separate person, with their own architecture of pain and habit, and that the project of love is to remain affectionate to that architecture rather than to demand its renovation.

What is, after all, the alternative? The alternative is to spend the years of a marriage attempting, somewhat secretly, to make your partner into a different and better person; and almost no one in human history has managed to succeed at this. The other person remains, irritatingly, themselves. The energy spent on the project of reform is energy that is not being spent on actually loving them; and the great irony, which one only notices in retrospect, is that the more energy goes into the reform, the less affection becomes available — and the less affection is available, the more the other person retreats into the very behaviours one had hoped to reform. Have you noticed this loop in yourself, or in others? It is one of the most reliable patterns in long human partnership. The cure for it is not, generally, to try harder at the reform; the cure is to accept, without entirely giving up on growth, that this is who you are married to — this is the actual person, they are not a draft, they are the final version, and you will live, for the rest of your life, with the particular blend of warmth and difficulty that constitutes them.

Can you, do you think, love that version of them? The question is harder than it sounds at first asking. We have been raised on stories of love in which one's partner is fundamentally good with perhaps a single dramatic flaw that can be heroically overcome in the third act; real partners do not have a single dramatic flaw, they have approximately a hundred and fourteen smaller and less dramatic ones, woven in with their many strengths; and the smaller flaws do not get heroically overcome, they get either accepted or they do not. There is, in the end, no third option.

What might it mean to accept them, in this sense? It does not mean to approve. It does not mean to pretend they are not flaws. It means, more humbly, to stop being shocked. To stop running, every Tuesday, the internal report titled "Surprising News About My Partner's Habits" and being indignant at the contents. The contents are not, after all, news. You have known about them for years. The only news, really, is that you keep being surprised by them. What might it be like to stop being surprised? It would, I suspect, be a tremendous and unexpected relief — and not only for you, but for them. Most people in long relationships carry, often without articulating it, the quiet weight of being slightly more loved if only they would, in some small specific way, change; they feel themselves, often unconsciously, to be on probation; they feel that some part of who they actually are has not yet been fully accepted into the marriage. To be released from this — to be told, in effect, "I see who you are; I am no longer hoping to swap you out for an upgraded version; I am, instead, here for the actual you" — is among the most precious things one human can offer another.

Have you given that to your partner, do you think? Have you received it from them? If the answer to either is "not yet", perhaps the project of the coming year is not, after all, to fix any particular item; perhaps it is something quieter — to look, slowly and properly, at the actual person sharing your kitchen and your bed and your decades, and to think, with some surprise — "this is who I love; this one; not the upgraded version; not the post-reformation version; this person, with all the same old things, the cupboard door, the clumsy phrase, the bad Tuesday, the long history of unhealed weather". Could you let them be that person? Could you, by the same generous extension, allow yourself to be the equivalent person on the other side of the bed, without continual apology? The madness of love is, in the final reckoning, the madness of two flawed humans consenting to remain near each other for a long time. It is not a tidy project; it is, however, against the long arc of a single life, very probably the most surprising and softening thing most of us will ever do. And at two in the morning, in the quiet of the dark room, when the argument has at last dissolved into something smaller, that is, I think, what you have been doing all along — loving someone who is, like you, magnificently and ordinarily mad.