What instrument?
I “play” violin and piano as hobbies.
Agreed. While I didn’t study music in uni, I did most of my practicing as a youth and now am able to return to a previous level without too too much work. Haven’t done much solo gig work as a violinist (none as a pianist), mostly ensembles. But I was just asked to play in two different weddings in June, so I should probably break out and practice a little. 
4 kids, 5 and under. I also like my hobbies at a high level and tend to operate at 110% or nothing, which drives my wife nuts. 
I like the rocking chair test mentioned by @awoffinden. Definitely need to find out what your priorities are and try to align your schedule, on a daily, monthly, annual level. And like several mentioned…things may have a different order of priority depending on the season of life you are in.
Not sure if I’ve said this before 
(Let's see your Steel builds! - #83 by mackeenj), but having a cargo bike with a power meter and several good training loops nearby allows me to take the kids out on my workouts, get them out of the house and into nature, give my wife a break…