What's your "Side Hustle?"?

I realize this sounds like a silly question, but please bear with me. A "hustle" is what we do during normal operations. In the civilian sector, we call it a job or a career. For the military, it's from reveille to taps. The thing that makes us more tactically and technically proficient.

A "side hustle" therefore is what we do outside the "hustle" in an effort to improve our lot in life. Civilians do it to earn a little more money, or make themselves more valuable, so they can make more money, improving themselves.

The thing about a "hustle" is that you will only ever get incremental gains. Now, incremental gains can end up being amazing over time.

http://freakonomics.com/podcast/in-praise-of-incrementalism/

But for immediate returns, we should always strive for exponential gains, hence the "side hustle" which doubles our productivity. Having a secondary thing we are doing to improve ourselves.

Before anyone goes "But K, this is the military, you shouldn't be getting a part time job!" That is not what I am advocating. What I am asking, is how are you IMPROVING yourself in your offtime, specifically outside of a military context. That doesn't mean it won't help you inside a military context (like a college degree), but what are YOU doing with the explicit goal of bettering YOURSELF?

This can be anything. Anything at all. From running a Non-profit, to writing a book, to going to college, to learning to cook. But something with purposeful practice designed to improve yourself outside of your primary "hustle."