what's the best habit you've developed and how did you develop it?

Not sure if best, but:

• cleaning the kitchen in the evening. I listen to podcasts or music while doing it, and the mornings are easier as I don't have to confront mountains of dirty dishes.
• reading - I try to dedicate at least one hour a day and read a book. I guess with general decline of the content on the Internet it got much easier to go offline.
• meditation and relaxation techniques - I started doing this as a teenager and thanks to hours I've put in I have no problems falling asleep. Even when I am high on caffeine I can relax my body during the night and wake in the morning not feeling like a zombie.