As someone that is unable to keep any sort of routine, I have objections here. :D Without some sort of obligating circumstance, it is incredibly easy to forego what would have otherwise been today's routine.
This 100x. I go to work because I don't want to have a long uncomfortable conversation with my boss, and because I hate interviewing, and not having income is even worse. Even at work, I often find reasons (like HN) to do actually DO work.
I've had routines at times in my life for months. And they disappear in a matter of days when I get stressed or my schedule changes or whatever.
What worked for me was a thing I started with one of my best friends, where we're accountability buddies for each other. We both pick topics/habits we wanna foster and then talk once a week about how that went the last week. In my case I chose exercise (going a certain number of times per week), and there were quite a few moments already, where I'm sure I would've just skipped if I didn't have this construct. It basically created this social obligation to keep the habit. I can really really recommend it if you wanna try it out with someone.