Has to be writing.

Not exactly a better dev, per se, but close enough.

I used to read books and imagine all sorts of possible scenarios to different events. One day, after replaying the Mass Effect series, I began to think about alternate ways to end it. Opened Libre Office and started hammering away. 10 minutes later, I had an outline. Never actually finished that story, but the spark was there.

I began noting down outlines and creating structures for interesting games and books; that soon carried over to my work. Before and after every meeting with my boss, I'd have outlined how the meeting was going to go, and how it actually went. Gave me a sense of order.

This in turn helped me be a better manager (I work with a team of 9), and I tell you guys, it couldn't have come at a better time. I had been promoted quite suddenly, and had been fucking up quite a bit at the start.
I had my shit in order. My team was happier and more efficient. My boss was happy. I was given bigger goals and tighter deadlines. I fucking loved it.

All this, from writing some fanfiction. (there, I said it!)

P. S: I stared at this for a solid minute, still not sure how it all came together.