When my cats aren't happy, I'm not happy. Not because I care about their mood but because I know they're just sitting there thinking up ways to get even.
Different men seek after happiness in different ways and by different means, and so make for themselves different modes of life and forms of government.
I usually say the aim of life is to be happy. Our existence is based on hope. Our life is rooted in the opportunity to be happy, not necessarily wealthy, but happy within our own minds. If we only indulge in sensory pleasure, we'll be little different from animals. In fact, we have this marvellous brain and intelligence; we must learn to use it.