I agree that peoples’ ‘normal’ energy levels vary enormously. I don’t think of myself as high-energy in particular, but I have a friend (a perfectly healthy man in his early 50s) who regards my normal week (I work FT, have a young child, am project-managing a big house renovation, walk or cycle everywhere, volunteer one shift a week on a helpline, and see friends and family), as an insane pace of activity.
I was a bit taken aback as I got to know him at just how low-energy he is — we have the same job, and he’s divorced and only has his children periodically, but he gravitates to the sofa when not actually at work, and something like taking his kids to their swimming lesson on Saturday is regarded as a huge and exhausting ordeal. I recommended he have a health check-up, but there’s nothing wrong. That’s just his ‘normal’.
I also have friends who are way more high-energy than I am. I have an architect friend who has three children, works 80 hour weeks and still trains for and runs ultra-marathons.
I write novels, and I’ve lost count of the number of people who tell me they would love to write, but haven’t the time. The truth is, you’ll fit it in somewhere if you want to, whether that’s getting up at 5 am, writing at lunch break at work, no longer watching TV etc.