It's a dark, overwhelming place sometimes. And a lot of us suffer alone because we are ashamed. We feel stupid. How can a person be incapable of having fun? Any moron knows how to have a good time.
It's almost impossible to talk about it to regular people (bosses, spouses, friends). They can't fathom how somebody in good physical health, with a good job, with kids who love them, who seems relatively normal on the outside, can be terminally unhappy.
And when you try to explain it, you come off sounding so pathetic, so weak and whiney, even to yourself — it's just easier, though infinitely more harmful, to suffer in silence.
With depression, there are no bright colors. A good day is a light gray or a muted blue. Most days are just gray. A bad day is pitch black.
So no, don't just say, "You're choosing to be unhappy." Don't say, "Just smile." Don't say, "Suck it up, what could you possibly be unhappy about." If that's on the tip of your tongue, then just - don't say anything at all.