Alittleprivacy, that sounds such fun! And quite an amazing achievement
I started playing tennis in my 40s, made loads of new friends, got fitter than I have ever been. Play almost daily now.
Kids are teens now, parents elderly and frail, DH has health issues but is ok for now and also fit and happy
I realise daily that everything can change at any moment, your whole life can come crashing down just like that. Friends have died, one is in terminal stage of cancer, strokes, divorces, depression, it all happens to people in their 40s it seems 
It has made me seize the day, as tomorrow it may all be gone. Strangely this has not depressed me but made me enjoy every moment there is to enjoy
Grey hair and wrinkles and varicose veins.... yeah so what, that does not bother me 
For me 40s have been a good decade So far. But yeah, that can all change at any time...