This particular habit I've been cultivating for over five months. I stopped for a week because I was insanely busy, and I'm taking a break from my medication. I couldn't motivate myself to do it after going off, and I was worried I was only doing it because I was medicated. I'm happy to say I'm doing it today to prove myself wrong.
The trick to that is to replace one bad habit with another (preferably less-bad) habit, that last bad habit was getting kinda boring anyway.