I think it's about long distance relationship: they can only see each other once in a while and every time it feels like they start from scratch and it is not a reassuring feeling. So he's saying, I want it all different because I'm tired of thinking (in the brief moments that they got together) you will soon leave. And it's hard to be carefree if the time is very limited and probably one is happy even with very little, and the other wants more instead, and he's in a sense a bit annoyed that they don't both want more.
I think it's about long distance relationship: they can only see each other once in a while and every time it feels like they start from scratch and it is not a reassuring feeling. So he's saying, I want it all different because I'm tired of thinking (in the brief moments that they got together) you will soon leave. And it's hard to be carefree if the time is very limited and probably one is happy even with very little, and the other wants more instead, and he's in a sense a bit annoyed that they don't both want more.