I think the thing with depression is that it quickly becomes uncontrollable. Everyone feels depressed at some point in their lives, even so-called happy people. You fail a test, you get yelled at by your superior, it rains on your wedding (or a black fly in your... nvm), shit happens. And people feel sad. But then you get better. Something cheers you up. Or you forget about what bothered you.
But what I'm feeling is different. I feel anxious or nervous for no real reason. I can try to figure it out, as most of what that post was trying to do. I'm definitely not happy with what I've done with my life, that's for sure. But someone else could look at my position and say, what the fuck? This guy's got nothing to be depressed about. I have a somewhat loving wife, a decent paying job, a good group of friends and a family who's mostly healthy. That's all true. And I know that, on some level, my life is probably pretty great. I try to tell myself that when I start to feel like shit. And while that used to work when I was younger, the power to rationalize away these feelings has dwindled to nil.
That's my problem.
Of course, today, I feel fine.