" can be used with one or more persons. But it wouldn't be used if one of those persons was depressed It is usually said when two or more people are having an alcoholic drink, It is a way of celebrating the fact that we are all well and are enjoying the drink. " to mean that you wish the person would become more cheerful.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.