Are you ‘mooning over’ somebody?

Over the moon: extremely happy

Many moons ago: a very long time ago

Once in a blue moon: something that occurs very rarely

Cry for the moon: to ask for something that is difficult or impossible to achieve.

Moon over (somebody): to spend time thinking about somebody that you love, especially when other people think this is silly or annoying. You use this to mean ‘pining for’ someone.