1. A lot of people would chop their arm off to make the money you're making that soon out of school. A 65% savings rate will add up before you know it.
2. You can change things about your work situation as others have pointed out (e.g., standing desk, walking desk). As I've found, we often have more power to change things - even in cubicle land - than we realize. I've been consistently shocked to hear a "yes" answer to my requests for more flexibility, different assignments, working from home, etc. But, you just have to provide a solid rationale for your employer on how it benefits them too.
3. Your current job can lead to better things, but you'll have to figure out what those things are and then go after them.
4. Related to that, if you build up your work experience and skills, you can eventually consult/contract/sub on your own as galaxie suggested. That was my path, and now I love my work (and the pay and hours are better to boot!). I highly, highly recommend this route, but it will require paying your dues and doing some time in the trenches/cubicle.
5. Being a bike messenger is one of those jobs that those of us who like bikes romanticize, but I suspect that the reality is that it can actually be pretty shitty, and worse, low paying, high-risk shittiness when you have to do it day in and day out.
6. You've only been working since 2012. I'm sure that there's someone that loved their first job out of college, but I haven't met them. You're running a marathon not a sprint, so remember, first job can lead to better jobs that you do enjoy if you work to make it happen.
7. Aside from all that, congrats on making one hell of a start. I wish I had my head screwed on as straight financially as you do when I was your age.