I'm in a great mood.
Every once in a while everyone just has a great mood. For some it's because their medications have finally balanced out, their cafe mocha with extra sugar just kicked in or the heroin they just injected is of a better quality they expected. For the less chemically enhanced it could be the sight something sappy like a velvet painting of a kitty, a poem written by someone with no talent or a birthday card signed by fifty people who don't know or care about them.
For me I know what it is that puts me in a best smiling for reason kind of good mood. And that's somebody in a bad mood. When someone I know is in a foul way it triggers some hormonal response in me that causes me to perk up. I don't think I'm actually happy that they're miserable I think it's a survival skill designed for couples not to completely fall apart by allowing both of them to be rotten at the same time.