I think it's because when you spend a lot of time with someone, you start to notice all of their annoying quirks you don't usually see when you just met them. S

I think it's because when you spend a lot of time with someone, you start to notice all of their annoying quirks you don't usually see when you just met them. So after a while you start to get tired and annoyed of them, and the way to deal with it is with anger.