True, it's impossible to make everyone happy.
It's hard enough to make just one person happy; even of that person is yourself.

What is happiness anyway?

Heh but I think it's important to never take unhappiness as a given, as something that can't be helped, and become apathetic to it, when it manifests itself in either yourself or those around you. That'd be monstrous. And it's all too easy to do so; at times.