You're apparently in a good place so looking back is your path to your joyful present. I'm in a bad place so looking back is my seeing back when I was still hopeful for my various life goals. I'd meet someone and have someone to share my life with, do activities with, travel with, raise kids with, etc. I never met that person and now at 60+ that's nearly impossible so looking back hurts. It hurts a-lot. Seeing the opportunities I missed, the time I squandered, the naiveté that "it will happen when it happens" etc.. I absolutely want to strangle Google/Apple/Facebook when they shove "memories" in my face. I didn't ask for it, piss off!

As for the topic itself. The obvious reason time passes faster when we're older to me is that each day is less of my life. At 1 week old a day is 1/7th of my entire existence. At 60 one day would be 1/22000th of my life.

I also feel it in terms of time left. When you have $1000 in your wallet, splurging on a $50 meal might seem fine. When you've got $75 in your wallet you're unlikely to blow $50 of it on a meal (unless you've got a supply elsewhere). In the same way, when I've have got 20yrs left in my life, some of them probably not in the best of health, then committing 10 of them to move to a foreign country to immerse myself in a new language feels very different than when I've got 60 years left (20yrs old). Seeing your life left clock go down 1/60th (1yr at 20yrs old) feels slower than seeing it go down 1/20th (1yr at 60yrs old). that's 3x faster.