Tough time. Growing up SUCKS no matter how cushy the job is.
You got a head start, too- I graduated college in my early 20's so I had a few more years of playtime before I had to get down to work.
And it sucked. I found a career and job that I liked but didn't pay much. I worked my @ss off, enjoyed my work... but didn't have much time or inspiration to write new music. I think I didn't really write much for 3 or 4 years. The cool thing, though, was that I could finally afford to buy a thing or two. A condensor mic... a compressor... a mixer...
It takes a little while to get it down, but the 9 to 5 isn't killing you. YOU are killing yourself because you haven't yet learned to keep yourself alive. Keeping yourself happy and healthy is a lot more than just putting food on the table. It takes a while to figure out what you need to do to keep yourself happy and inspired.
For me (and its different for everyone) it was taking walks, getting to know the plants and animals around where I lived, spending as much time outside as I could. For some reason that kept me feeling alive and inspired. I also got really into getting to know the people I worked with and enjoying my interactions with them at work. My line of work made that easy.
Keep a journal. Write about what you're feeling and what's going on for you. I don't care what you write, JUST DO IT. The act of writing anything regulalry will help you sort through your depression AND will keep your mind flowing in the mode of creativity. I don't journal as much any more but it kept me alive when I was going through the same thing you are.
I also made an effort to keep learning new things. I'd sit down with the studio stuff to just start using some new technique or trick I'd read about and figure it out. That would be my excuse to MAKE time for music and not care too much about writing the next great hit. Between learning something new and just spending some time with my hands on the guitar... I would regulalry stumble across stuff that inspired me.
It takes a while to figure out, but I *love* being an adult, living on my own and making my own choices. Yeah, you're a bit whiney- at least you COULD save up enough making that kind of money to take a year off and go wander. And that might be a good idea if you're *sure* you will never be happy on the path you're on now.
I'd say give it at least a year, though. For one, if you stay at a job for at least a year it doesn't look as bad on your resume when you try to get a job later. For two, give yourself the chance to learn how to live this way. Its a skill that takes time to learn like any other- and its a really damned important skill.
And props for knowing that "very idiotic things seem like good ideas at 19." With that statement alone I know that you have enough insight to figure this out. I didn't learn how stupid I was until my mid-20's.
Take care,
Chris