Real or not

Something I find fascinating is the way I can still laugh at something even though I am sad, or depressed, or empty. I mean, when I have time to think about things and let my mind wander those feelings surface and are so real that I almost can't breathe. Yet, when I am concentrating on something else I can still laugh.
I mean I shouldn't be laughing right? I am quit sad. Yet I do, it is a strange and in a way wonderful but disturbing thing. How can two conflicting emotions live side by side so explicitly and remorselessly? Is it something in me? Is it because I don't feel anything no way near as intensely as before? No, that cannot be the answer because I have experienced this duality before. The reality of the situation surprises you like a rainbow after a rainy day. Amidst all the sadness and confusion and frustration there is still strength left inside to laugh and keep going and carry on with your live.
It's a strange parallel I find with the film Sex and the City I watched recently, the corniest film ever, but even that is surely based in life and life experiences. When something that brakes you heart happens you think it is the end of the world, or you want to think that it is because you cannot envisage a way forward, and yet the way comes to you somehow regardless.
As somebody once said, Life finds a way, maybe it's a survival mechanism our genes have developed over the aeons to deal with unexpected and unpredictable change.