I think a lot of women have a kind of mini mid-life crisis in the years between 40-50! Partly hormonal, partly psychological, 40 is some kind of demarcation line between 'young and pretty' and 'old and past it' and when you get that prod from mother nature/society's expectations/the cruel mirror, it's a little shocker, ain't it!
If you've had a very enjoyable life, caned the booze, smoked too many bifters, baked in the sun, spooned nutella out the jar most evenings, been overworked, sleep deprived, are almost always undernourished, dehydrated, sick, whatever, it definitely starts to show as you get older. And usually on your face.
You can just let it slide, if you want. Smash the mirrors in your house. Only use candlelight at home. Stop plucking your eyebrows, eat more cake, buy sensible shoes, stop dyeing your hair. Most of the people who know you probably won't give much of a toss. There's millions of overweight, mushy-faced middle-aged people in uncoordinated anoraks and polyester slacks who look like they've given up. They have. It's okay. Nobody dies.
(Except the fashion fairies. Oh yes. Every time a middle-aged woman buys American tan tights and gets a 'helmet' perm and keeps the same handbag she's had for twenty years, the heart of a small, well-coiffed Chanel-clad fairy breaks...I thought everyone knew that!).
But yeah, if you don't want to succumb and become 'one of them invisible wimins'... there's loads of things you can do. Some people choose injectables, some people start diets, some people buy new wardrobes, and some have total life revamps, dump their old fellas, change careers, get new lovers, take up new hobbies, start charities...
Tis up to you...