It’s all about the first drink, as in the first drink of your life and the first drink of the day. This much I learned in writing a book about drinking less, which involved examining how I came to be drinking so much in the first place. And I trace it all back to a thoroughly miserable fortnight in Germany when I was 14.

It was a school exchange. I was paired up with a lad I’ll call Siegfried. We had nothing in common. This was entirely my fault, because in the week we filled out the form about our interests, I had taken up chess. I duly declared chess to be my main interest in life. It wasn’t. My main interests were football, music and the unrequited adoration of a succession of girls. I quickly realised I was hopeless at chess and gave it up but, by then, the wheels of the pen-friend selection machine were turning. It needed no particularly great application of Teutonic logic for me to be paired up with the German school’s chess champion.

Poor Siegfried looked every inch the school chess player. He wore the kind of glasses that make your eyes look bigger. I too wore glasses, being shortsighted, so I suppose we did have specs in common, but that was it.

For me, the whole trip had fallen apart the day before it started. When I got home from school, I had the strongest sense that something wasn’t quite right. Before long, my dad was telling me that my grandmother in Croatia was gravely ill. Baka, as I called her, had had a stroke at home in Zagreb. My mum was speaking urgently to her sister there on the phone. I was close to my Baka; she spent every Christmas with us. I really didn’t want to go on the stupid German exchange. I was terribly upset and anxious, and it was already clear from the correspondence between Siegfried and me that he wasn’t my type.

But Mum and Dad decided I should go. I fervently wished they hadn’t. I’d never been so miserable in all my life; come to think of it, I’ve not been so miserable since. Never have two weeks passed so slowly for anyone, ever. The school was in a town called Leonberg, near Stuttgart. I got on with Siegfried every bit as badly as I’d feared. I looked longingly at my fellow schoolmates, all having wonderful times with their new friends. The German girls were conspicuously beautiful and plainly uninterested in either me or my fellow spectacle-wearer. We shambled wordlessly home. To his bafflement I refused all his offers of a game of chess. Eventually I relented just to show him how clueless I was, which didn’t take long. No more chess was played.

I was so homesick it physically hurt. To make matters worse, a couple of days after I got there, my mum called. She said: “The situation in Zagreb is unchanged, and we’re going there tomorrow.” The situation in Zagreb is unchanged? It sounded like something a news presenter might say. My mum just didn’t speak like that. I knew that my Baka had died.

I sank still lower. Siegfried’s mother was a lovely woman who tried everything to cheer me up, without success. A friend from home sent me a press cutting about Bryan Robson, my team’s best player, being sold to Manchester United. If it was possible to die of sheer unhappiness, this would have been the straw that broke the camel’s back and saw me draw my last breath.

I have scant memory of any of the excursions our exchange group were taken on, bar one. In the second week we went on a tour of Leonberg’s brewery. I moped around, disliking the smell, looking on without interest as we were shown how beer was made. At the conclusion of the tour, we were sat down at long tables and given what was probably rather strong lager to drink. I didn’t much enjoy it but, within a matter of minutes of it coursing through my veins, I was going through some kind of emotional transformation.

It felt so good. At that moment, the last few days we had left on the exchange went from feeling like an eternity to something wispy and insignificant and even possibly enjoyable. I laughed and joked with my friends and even fancied I spotted a girl called Claudia looking at me. And I became overwhelmed with sorrow for poor Siegfried, who couldn’t face more than a mouthful of beer but, with unbearable sweetness, was plainly delighted to see me smiling.

Waves of wellbeing crashed over me. And this at a traumatic moment in a critically formative phase of my life. I’d never had to deal with the death of a loved one before. I was going through shock, bewilderment, fear, loneliness and terrible, gut-wrenching homesickness. I was in pain. But one draught of this strange brew took that pain away. In the matter of a few minutes my whole world had been reframed. It was magical; why wouldn’t I want more of the same?

Forty years later, having put petrol-tanker quantities of alcohol through my system, I see the significance of that first drink. And, more importantly, the significance of the first drink on any given occasion. The first one is the only one that matters; it’s the only one that brings about a wondrous change in your emotional state. All subsequent drinks are increasingly fruitless attempts to recreate that initial feeling. Grasping this truth is the surest route to drinking less. Relish the first drink, and perhaps a second if you must, but don’t bother with the rest.

• The Good Drinker by Adrian Chiles (Profile, £14.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply. Adrian will be speaking about his book on 15 October at 5.30pm at the Ilkley literature festival. To book, click here.