Now I have kids, a house, dog, so many things to think about, so many things to do. I start working at 9am and I am already tired due to all the obligations I had since I woke up. I make very stupid mistakes I didn't do before. The time it takes me to complete tasks is much slower than it was before.
Yes there is the added experience and skills and everything, but I think that for most situations, now-me is just a crappier developer than past-me, and I can't see in my horizon any possibility of me going back to what I once was. I don't think I will ever be as motivated as I was before.
Do you people share this experience?
I also make a lot more money now than when I was younger, even adjusting for inflation, and I work about half the hours I used to. I can get more done in less time because I rarely encounter a novel problem (in typical business apps and web sites, anyway). I see the same problems over and over with different clothes on.
I am no longer able or (more importantly) interested in working 18 hour days. Like you, I now have a family, a house, pets, etc. All of them get time that was previously available for coding (and partying).
I can no longer focus as well as I could, my memory is less good, and my ability to hold concepts in my head is more constrained than it was when I was younger.
OTOH, I know a heap more. In purely technical areas, in the business domain I've ended up in, in working with people, in .. so many areas.
I am absolutely a different value-proposition to an employer than I was 20 years ago. I'm a very different employee -- not better, not worse, but suited to different aspects of the work at hand.
Motivation comes and goes. I don't find it hard to get passionate about things, but I realize now that most things are a marathon, not a sprint. A deep commitment ends up beating a flare of passion that moves on quickly to something else.
Also, burn-out is a thing for me. Not the debilitating kind (although that's totally a thing too) but the more insidious kind where you skim along, dipping in and out of the danger zone, propped up by good challenging projects, awesome co-workers, and vacations; but weighed down by stress, and bad projects, and working with jerks. Figuring out when that's happening, and how to turn things around, took me a while.
All just my views, YMMV, etc.