The human condition has been termed and interpreted in so many ways. Various aspects are thought of and wondered about, but enough can't always be certain that certain things are across all humans. Really, the human condition is just...random... We're emotional creatures, who try to fight that emotion with logic. Which wins out? At least in my case, emotion does. There are some who can override emotion with logic, then there are those who simply are incapable of feeling any emotion; the latter being sociopaths, so I won't go too much into that. But for people like me, emotion wins out...roughly 90% percent or more of the time.
Little things can bring people down when they're in a low mood. Little things can stack up until they topple over and cause someone to fall down into a bad mood. Logic can tell someone to not worry since it's...life, you can't do anything for it. But emotion? Well that's the bitch that makes things difficult depending on what level you feel things. Some people can hide behind a shield of apathy, but have little things that can make the feelings of guilt and remorse resurface. Some only have that issue when it comes to people they care about. Long days can make some who already feel not so great feel worse. Things not working out, can make people feel awful. Life just...going on and being life as it is, can make people slip and fall however low they may go.
This is not about depression, but of simple low points that people feel at times. It hurts, but it's just how things are. If you're a logical person, good for you, glad you can override whatever. If you never feel low points, congrats. But for people who can slip into funks that last a couple days, maybe a week or so, that's life. Knowing that doesn't make things better, but so long as the knowledge that it will pass, that you can get on out of that pit of sadness or whatever soon, that, if you upset someone in a generally minor way (like saying something not too detrimental, not...saying they should kill themselves and honestly meaning it, or, hell, even not meaning it) that they will get pass that, too, so you don't have to feel guilty anymore. And always remember the bright spots there; be it seeing and laughing with friends, or just taking some time to relax on your own.
I'm not an optimist by any means, but hope is something that is part of the human condition, I think. You need hope to tell you that things will pass, that you won't want to curl up in a corner someplace for the rest of your life, that...whatever surrounds you is not permanent. If it weren't for hope, everyone would fall into serious depression, not just bad moods. Hope is the line between being broken and being held together.