Here's how I've been able to do that lately, even now that I have to be a so-called real adult.
1. Fashion. The great thing about working for a company whose dress code is business casual is that I still have room for self-expression. Below is my outfit from casual Friday: I rocked a Hogwarts tee under my blazer and paired skinny black jeans with my studded combat boots (sorry no full outfit photos!). A blazer dresses anything up...right? I always have my skull or Slytherin jewelry on daily with my button-ups and pencil skirts, along with a (slightly) more subtle smokey eye than my usual gothed out eyeliner. I can enjoy my job so much more when I can express myself in these little ways.
2. Sword fighting. Nothing like a new hobby to spice up life a bit. I scored a Groupon for Medieval Combat lessons, and as it's been my ambition to become a pirate lately (and I'm writing a novel featuring pirates), I figured what better way to get into character than to learn some good old sword fighting. I'm completely addicted. My coworkers like to give me a hard time about this. I think they all thought I was kidding at first...
3. Developing my "personal brand." We've talked a lot about this at work, and while I've wanted to obviously present myself as competent, I think part of my, er, charm is that I'm kinda quirky. Everyone already knows me as the resident Harry Potter nerd (I showed up with the seventh book in my purse on the first day of training and admitted that I was in the process of my annual re-read of the series). When we had to go around and introduce ourselves and say a weird fact, I announced that -- though I used to be super embarrassed about admitting it -- I've been a Harry Potter fan fiction writer for ten years. I got a bit of playful teasing, but once again, I was hardly shunned because of it. I want to present myself as quirky, nerdy, and smart, a brand I feel like will let me be successful while still feeling like me.