My best productivity habit has been using https://crushentropy.com/ every day. I wrote it for myself but a lot of people use it now.

It's like markdown for high resolution planning.

I used to feel harried trying to cram a lot into the day. Now I spend a few minutes planning the day and when I'm in a certain time block, I can totally relax, not worry about all the other things I need to get done in the day, and really focus.

If the day changes due to interruptions etc, I type that in and the rest of the day reflows around that.