I think there comes a certain point where you realize not only that time is precious and limited, but so is energy. Your own energy. Everyone can say something similar to this, I'm sure, but I remember when I could stay up late hanging out with people at my local bar, drink there, get about 6 hours of sleep, wake up and play two hours of morning tennis - singles - and then come home and write for four hours before going to my night job. Not so anymore, though I still do average about 5 to 6 hours of sleep a night, on weekdays at least. I reserve more time for sleep on weekends.
But my point: energy. It's difficult to do at 57 what you could do at 37 (which is the period I'm talking about with the hanging out and then getting up to play tennis, etc), and anyway, that was before marriage and kids. Then mornings are completely taken up for years, and you might find yourself, as I did, squeezing in hours whenever you can after dinner and after everyone has gone to sleep. That's tough, and I've touched on it here before, methods employed like drinking coffee late at night, napping briefly right after the coffee, and setting the alarm for 20 minutes later when the caffeine is kicking in. It works, though it can be difficult to shut yourself down later at night and get back into bed for the sleep needed for a coming day of work.
Regardless, my routine has changed once again, thanks in large part to the new availability of early mornings. Now the onus is all on me to get to bed early enough (11 to 11:30 is good) so that I can wake by 5 to 5:30 to get in some work before I go to my job. I have to stop myself at 8 usually to be at my job on time. I have the coffee machine loaded, the timer on, and all I need do when I get up from bed is pour myself a mug.
Are there days when I find it hard to drag myself from bed so early even if I went to sleep on time? Of course. But this early morning routine, writing when the mind is clear and the energy level is high, beats the exertions I sometimes had to go through to get anything done at the end of a day. I carry the same principle over to most weekend days, though I don't have to get up and get to my laptop quite so early on a Saturday or Sunday.
Listen to your body, a lot of athletes say. For a while now, I've been able to do that, by working early mornings instead of late at night, and I'm enjoying this more productive use of whatever energy I have.