You try to ignore the early signs. The disconcerting weight gain that means old favourites no longer fit and old styles no longer suit. The loss of interest in cherished pastimes; the hours of wakefulness while the household sleeps.
Then come the secret stashes of comfort food, exhausted afternoons behind closed curtains. There's the apathy, the anger, the addiction to soaps in the need for escapism.
What keeps you going are the highs. The sudden flaming enthusiasms, companionable shopping trips, heart-to-hearts in the bedroom and, always underlying, that intoxicating sense of possibility.
The change of life is a frightening thing. It requires total adjustment of everything you took for granted. You have to rethink the way you communicate, the way you think, where and when and how you go. You know the future depends on how you cope with it. It's a balancing act between holding out and letting go, speaking or silence, cosseting or independence.
What they don't so often tell you is that, in its vividness and unpredictability, it's glorious. And today it happened to me. For the first time, I have become the mother of a teenager!
Happy birthday to my no-longer-little girl.