I hope you are well. I know you are not. As it happens you wrote in 1973 a letter to your future self and it is high time that your future self had the decency to write back. You declared in that letter (reproduced in your 1997 autobiography Moab Is My Washpot) that "everything I feel now as an adolescent is true". You went on to affirm that if ever you dared in later life to repudiate, deny or mock your 16-year-old self it would be a lie, a traducing, treasonable lie, a crime against adolescence. "This is who I am," you wrote. "Each day that passes I grow away from my true self. Every inch I take towards adulthood is a betrayal."

Oh, lord love you, Stephen. How I admire your arrogance and rage and misery. How pure and righteous they are and how passionately storm-drenched was your adolescence. How filled with true feeling, fury, despair, joy, anxiety, shame, pride and above all, supremely above all, how overpowered it was by love. My eyes fill with tears just to think of you. Of me. Tears splash on to my keyboard now. I am perhaps happier now than I have ever been and yet I cannot but recognise that I would trade all that I am to be you, the eternally unhappy, nervous, wild, wondering and despairing 16-year-old Stephen: angry, angst-ridden and awkward but alive. Because you know how to feel, and knowing how to feel is more important than how you feel. Deadness of soul is the only unpardonable crime, and if there is one thing happiness can do it is mask deadness of soul.

I finally know now, as I easily knew then, that the most important thing is love. It doesn't matter in the slightest whether that love is for someone of your own sex or not. Gay issues are important and I shall come to them in a moment, but they shrivel like a salted snail when compared to the towering question of love. Gay people sometimes believe (to this very day, would you credit it, young Stephen?) that the preponderance of obstacles and terrors they encounter in their lives and relationships is intimately connected with the fact of their being gay. As it happens at least 90% of their problems are to do with love and love alone: the lack of it, the denial of it, the inequality of it, the missed reciprocity in it, the horrors and heartaches of it. Love cold, love hot, love fresh, love stale, love scorned, love missed, love denied, love betrayed ... the great joke of sexuality is that these problems bedevil straight people just as much as gay. The 10% of extra suffering and complexity that uniquely confronts the gay person is certainly not incidental or trifling, but it must be understood that love comes first. This is tough for straight people to work out.

Straight people are encouraged by culture and society to believe that their sexual impulses are the norm, and therefore when their affairs of the heart and loins go wrong (as they certainly will), when they are flummoxed, distraught and defeated by love, they are forced to believe that it must be their fault. We gay people at least have the advantage of being brought up to expect the world of love to be imponderably and unmanageably difficult, for we are perverted freaks and sick aberrations of nature.They - poor normal lambs - naturally find it harder to understand why, in Lysander's words, "the course of true love never did run smooth".

Sexual availability, so long an impossible dream in your age, becomes the norm in the late 70s and early 80s, only to be shattered by a new disease whose horrors you cannot even imagine. You would little believe that I can say to you now across the gap of 35 years that we are the blessed ones. The people of Britain are happy (or not) because of Tolpuddle Martyrs, Chartists, infantry regiments, any number of ancestors who made the world more comfortable for them. And we, gay people, are happy now (or not) in large part thanks to Stonewall rioters, Harvey Milk, Dennis Lemon, Gay News, Ian McKellen, Edwina Currie (true) et al, and the battered bodies of bullied, beaten and abused gay men and women who stood up to be counted and refused to apologise for the way they were. It has given us something we never thought to have: pride. For a thousand years, shame was our lot and now, turning on a sixpence, we have arrived at pride - without even, it seems, an intervening period of well-it's-OK-I-suppose-wouldn't-have-chosen-it-but-there-you-go. Who'da thought it?

I know what you are doing now, young Stephen. It's early 1973. You are in the library, cross-referencing bibliographies so that you can find more and more examples of queer people in history, art and literature against whom you can hope to validate yourself. Leonardo, Tchaikovsky, Wilde, Barons Corvo and von Gloeden, Robin Maugham, Worsley, "an Englishman", Jean Genet, Cavafy, Montherlant, Roger Peyrefitte, Mary Renault, Michael Campbell, Michael Davies, Angus Stewart, Gore Vidal, John Rechy, William Burroughs.

So many great spirits really do confirm that hope! It emboldens you to know that such a number of brilliant (if often doomed) souls shared the same impulse and desires as you. I know the index-card waltz of (auto)biographies, poems and novels you are dancing: those same names are still so close to the surface of my mind nearly four decades later. Novels, poetry and the worlds of art and ideas are opening up in front of you almost incidentally. You spend all your time in the library yearning to be told that you are not alone, and an unlooked for side-effect of this just happens to be a real education achieved in a private school designed for philistine bumpkins. Being born queer has given you, by mistake, a fantastic advantage over the rugger-playing ordinaries who surround you. But those rugger-playing ordinaries have souls too. And you should know that. I know you cannot believe it now. They seem so secure, so assured, so blessedly normal. They gave Cuthbert Worsley the Kipling-derived title of his overwhelmingly important (to you) autobiography The Flannelled Fool: "these are the men that have lost their soul/ The flannelled fool at he wicket/ And the muddied oaf at the goal".

You look down at the fools almost as much as you fear them. The ordinary people, whose path through life is guaranteed. They won't have to spend their days in public libraries, public lavatories and public courts ashamed, spurned and reviled. There is no internet. No Gay News. No gay chatlines. No men-seeking-men personals. No out-and-proud celebs. Just a world of shame and secrecy.

Somehow, as you age, a miracle will be wrought. You will begin by descending deeper into the depths: expulsion, crime and prison - nothing really to do with being gay, but everything to do with love and your inability to cope with it. Yet you will, as the Regency rakes used to say, "make a recover" and find yourself at university, where it will be astonishingly easy to be open about your sexuality. No great trick, for the university is Cambridge, long a hotbed of righteous tolerance, spiritual heavy-petting and homo hysteria. You will emerge from Cambridge and enter a world where being "out" is no big deal, although a puzzlingly small number of your coevals will find it as easy as you to emerge from the shadows. Before you damn anyone for failing to come out, look to their parents. The answer almost always lies there. Oh how lucky in that department, as in so many, you are, young Stephen.

But don't kid yourself. For millions of teenagers around Britain and everywhere else, it is still 1973. Taunts, beatings and punishment await gay people the world over in playgrounds and execution grounds (the distance between which is measured by nothing more than political constitutions and human will). Yes, you will grow to be a very, very, very, very lucky man who is able to express his nature out loud without fear of hatred or reprisal from any except the most deluded, demented and sad. But that is a small battle won. A whole theatre of war remains. This theatre of war is bigger than the simple issue of being gay, just as the question of love swamps the question of mere sexuality. For alongside sexual politics the entire achievement of the enlightenment (which led inter alia to gay liberation) is under threat like never before. The cruel, hypocritical and loveless hand of religion and absolutism has fallen on the world once more.

So my message from the future is twofold. Fear not, young Stephen, your life will unfold in richer, more accepted and happier ways than you ever dared hope. But be wary, for the most basic tenets of rationalism, openness and freedom that nourish you now and seem so unassailable are about to be harried and besieged by malevolent, mad and medieval minds.

You poor dear, dear thing. Look at you weltering in your misery. The extraordinary truth is that you want to stay there. Unlike so many of the young, you do not yearn for adulthood, pubs and car keys. You want to stay where you are, in the Republic of Pubescence, where feeling has primacy and pain is beautiful. And you know what ... ?

I think you are right.

• This is an edited version of an article from the 25th-birthday edition of Gay Times, out now. For more details, go to gaytimes.co.uk