There it is, in a nutshell
I found this on another person's online journal. It's a long, involved story about the process of making a record, and it's funny as hell. But I was struck dumb by this paragraph, because it sums up a lot of what I'm going through right now:

And anybody that thinks I should blindly skip through life satisfied at being unproductive so long as I’m being compensated for such activities, isn’t considering the negative effect that lack of accomplishment can have on the brain. The act of accomplishing nothing other than wastefulness is both exhausting and debilitating to the soul. And while in the short term it may be self-serving to my financial well being to participate in such unproductiveness, the resulting waste only serves to sicken me.

I'm making a pretty good living, which is cool. I feel like I'm accomplishing very little, which isn't. The former really doesn't make up for the latter.