Gillian Anderson spent a day crying over the reality of ageing.
The actress admitted it is "arresting" seeing how she's changed on screen over the years and had to allow herself some time to "mourn" the person she used to be.
She told Vogue: "If you watch yourself on film, there is a certain point where you see yourself change. It's arresting.
"It can either be completely traumatic or something that instigates a shift of consciousness towards thinking about what's important. But you have to go through that trauma first, to mourn."
But the 50-year-old star has grown to accept that she can't do anything to halt getting older so is celebrating the changes instead.
She added: "The thing to remember is, how one looks in the mirror is the youngest one will ever look again. So you can't do anything but celebrate it!
"Ageing is something we all need to find a way to embrace - the inevitability of age, of decline, of... rot."
Gillian - who has children Piper, 24, Oscar, 12, and Felix, 10, from previous relationships and has been dating screenwriter Peter Morgan since 2016 - can currently be seen in Netflix comedy drama 'Sex Education' as sex therapist Jean Milburn.
She previously suggested her character's job is one she could have held in real life because of her own experiences.
She said: "Over the years people have often come to me for advice and I've certainly have had a lot of therapy. I could be a therapist."