The big difference is for the last 8 years I've put in 3-5 hours of hard exercise (powerlifting) every week before work. I wish I had more time, both for exercise and projects, but these days I can pull all nighters and walk into the gym 7am the following morning and set new personal records a couple of times a week, and keep my energy up all day, whereas at 30 I was worn down to the point where I couldn't walk up a flight of stairs without my knees hurting, and would collapse on the sofa in the evening and not have energy for anything.
Now I am in better shape than most of the kids half my age at my gym, and have early 20's body builders talking about how deep I can squat.
And I go home after work, play with my son, and put in time on my projects after he's in bed.
Sure, I had downtime when my son was smaller, but kids are not an excuse for all that long - when he was younger, I put projects aside and my only "me time" was focused on keeping fit, and I feel it paid off. Now, every day, he can do more stuff for himself, and wants to, and every new achievement means more energy left over for me.