Do you remember being so young as to actually believe the world was a wonderful place? Being so oblivious that you were happy? Don't you miss that?
To be happy now, it takes hard work. We must focus on the good so that the bad becomes a blurry haze. Perhaps our brains evolved to do that. For to live any other way would be much too painful. To think of all the crime, all the wars, all the horrible things happening to people everywhere! The knowledge should stupefy us. But it doesn't. We are entirely able to move on from anything. In fact, people actually begin their days reading about all the bad that happened in the world yesterday. And then have the nerve to say "Good morning"! Surely, they're being ironic!
I'm fairly certain we (voluntarily) suffer from selective amnesia. Think about it. Remember the good old days? Of course you do. The past is a world where roses bloom, and nothing bad ever happens. The present too, so long as it is far away from us, becomes not-quite-so-real. They are "other people's problems". And we are immune from them. Or at least, we believe we are. We have to.
Perhaps that is what separates the cynics from the rest. Maybe they see too clearly. Maybe they don't forget as easily. And then they wonder at the rest of us, content in spite of it all, and imagine that perhaps we are just ignorant. But we aren't. We just try our damnedest to be detached from the knowledge that would otherwise crush us with its ugly weight. Because, you see, ignore-ance is bliss!