Honestly, I feel the opposite, but perhaps I have lived in reverse.
What I find most interesting about your quote is this:
"I think a big part of it is, when you’re young the idea that in “the future” you could do anything/be anything/achieve something great, and probably will cos you’ve got SO much time. Then when you get older you (or I anyway) realise all those dreams aren’t going to come true cos they would have happened by now"
When I was younger I didn't really enjoy anything, just felt a constant need to achieve/ progress asap like time was running out. Certainly didn't live the life you describe, no nights out that I enjoyed, or weekend football tournaments for me. It was very much busy-busy-busy, ticking boxes for everyone else. Granted, I achieved most things people consider 'impressive' before 30, but that's beside the point.
I think completely differently about 'the future', achievements, and dreams.
I have about 20 working years behind me. That leaves me 30 good years ahead. If you look at when people achieve things, it's often not until they are 50+, e.g. starting a business, buying their forever home, writing a novel.
I think my 'worst' years are behind me, thank god, and think the best times are yet to come. I am not even in the middle of my adult life yet, at 40 you've pretty much just begun and smartened up, figured things out for what they are. It's like being at level 4/10 in a video game if we don't count years as a child.
Right now I get my 'thrills' from:
- Making all my childhood years dream come true, as at 40 you have the money. Even if it's silly things like seeing the Spice Girls live, visiting Timbaktu or wearing a pink Dior dress. I spoil my inner child
- Looking and feeling my best ever, as pace of life is calmer and taste in clothes and beauty so much better
- Culture - I never deprive myself from any theatre, art, museums, books, something I was too busy for in younger years
- Thinking about the future. To me, 10 years from now, I could be anyone, anywhere. Feel like I am learning and growing every day. Super excited about who I'll be at 50. I surround myself with really interesting people of varied ages and feel really inspired regularly
Oh and the sex is better than any previous decade I find. People finally vaguely know what they are doing and aren't so prudish!
By way of advice I'd say find some positive role models who are older than you. Not sure what you're into but for example Mel C gave a great interview about what 40 and 50 could feel like with the right mindset. Honestly, 20s and 30s to me seemed comparetively shite considering how 40 feels, and lots of women seem to agree.