Because

"I was sitting there watching you, realising that you were really happy at that moment, and your troubles have at least left you for that short while. I could feel a wave contentment washing over me just watching you smile.

In that very instance, I realise that if this is as good as it is going to get, it is just enough for me.

Because I just want you to be happy.

And because I am only happy when you are."