I actively did some crossfit a couple of years ago. It's not my thing at all (when I exercise at all, I tend towards obscure martial arts), and I absolutely hated it, but at some point I went 3 times a week, and I still don't entirely grasp how I managed that.

One thing that certainly helped is that after a couple of months, I really started to feel the impact. My back muscles in particular felt like steel cables at some point, and my posture significantly improved.

Then Covid hit and now I'm a weakling again. I'm trying to get some regularity in going to the gym at least twice a week. Monday was my first time in months. But the biggest step is making it part of your routine. Make it something you do without even having to think about it. Once you allow yourself to question it, the discipline breaks.