> It's probably a matter of this being a habit of a lifetime that I've never fought back against hard enough.
You could try what worked for me:
Make a list of 2-5 healthy habits or routines that don't naturally fit into your current rhythms. Things like being an early riser, going to the gym in the morning, finishing all of your work before 5PM, and so on.
Then, pick 2-week periods to try them out, one at a time. For example, I always thought I was a night owl and and had delayed sleep phase syndrome until I made a deliberate effort to go to bed at 9PM every night for 2 weeks straight. The first few days were painful, but it's easy to push through when you're only looking at 2 weeks maximum. After those 2 weeks, I realized I'm a much happier, healthier, and more productive person if I go to bed at 9PM and wake up at 5AM, but it doesn't happen naturally.
Alternatively, you may discover that a routine doesn't work for you, but you're not losing much by trying it out for 2 weeks.
On average, you have about 4000-4500 weeks in a life time. It's worth taking some of those weeks to run easy experiments that could pay dividends for years to come.