"My job is my hobby" can mean one of two things: you have not time for a hobby OR you think you love your job enough to be a hobby.
Although I fit into both categories, I considered myself of the later variety. I love to write, love creating story, love designing interesting concepts. However, I'm quickly realizing that can't be all that I do. By pursuing one thing solely, I may achieve excellence, but actually at a slower rate than if I integrate other activities. The reason is simple: the subconscious needs time to work.
Humans are processors. As such, we cannot run one program full throttle all the time without burning out. Computers are the same way. It's important to have rest, deviation, a chance for perspective. This is incredibly important for artists as the subconscious will work on your project for you while you do other things and may even solve problems for you in "Eureka moments." For those more technical, your job is very detailed. Taking a moment to look wide and rest your eyes will allow your brain to be more productive later.
So, hobbies are good. With moderate doses, they can make you more efficient, focused, and creative. Furthermore, if it's something you're good at or something you need to learn, it will develop confidence as you achieve mini-goals. It's stress-free, expectation-free you time that offers a chance for learning and growing at your own pace. This, in turn, wards of stagnation, burn-out, loss of confidence, and loss of interest. When one thing isn't going right here, it represents a place for something to go right.
Now, as I realized, the hobby selected does not have to be something you already love. In fact, it could just be something you want to try, are interested in, or what to be able to say you can do. Cooking, photography, knitting, painting, kayaking, fishing, etc. You may go through a few before you find one you want to keep setting goals with.
I chose rock climbing. Why? Because I can always use an excuse to move when most of my work revolves around a computer and those endorphins are wonderful natural happy-drugs. Furthermore, it's something I'd done once inside and once outside and really like both times. I liked the danger factor to keep me interested, the ability to do some many different types (top rope, lead, bouldering, outdoor, indoor, ice, sport, trad, etc.), and the community. I love the mental and physical puzzle it generates as you learn how to move yourself in order to get to the goal: the top.
It occurred to me the other day at the climbing gym that rock climbing is a lot like life (I think many hobbies can act as a life metaphor). There are difficult spots and easy spots. Sometimes you need help (chalk or your partner to hold you up as you rest). There can be high stakes and potential danger. User error can have devastating consequences. It about the relationship and trust you have with the people supporting you and finding the fun through the blisters, muscle cramps, and sweat.
It's provided me a place to focus on something new and return to my work refreshed, with a new perspective. It's given me challenges that are straight forward and directly reliant on my progress and ability, and it's given me a way to strengthen my skills in an multiple facets.
Hobbies are healthy when balanced into the system of life. What I thought would be a deterrent and a distraction has become a catalyst for achievement, learning, and excellence.