Once in a blue moon

How often do you see a blue moon?

Not very often?

Then something that happens very infrequently happens once in a blue moon.

E.G. 'Do you go to the movies very often?'

'Hardly at all; once in a blue moon.'

Of course, blue moon isn't just an idiom but a classic rock and roll ballad - like this:

Like a fish out of water

Do you sometimes feel like a fish out of water?

That means do you feel as if you are in the wrong place and not comfortable in your environment.

The rugby player felt like a fish out of water in the dance class - although sometimes people can adapt.

Anyway, although most fish stay well below the surface, there are some fish that like to feel like a fish out of water!

To lose the plot

The plot is the story line or sequence of events in a book, film or play. If you lose the plot, you lose track of it and you can’t follow it.

As an idiom it is a metaphor, usually for someone who has lost touch with reality.

Here’s a sixties icon who lost the plot big time, Syd Barrett, founder member of Pink Floyd, in a rare interview.

After a summer of continuous LSD use, he’d shattered his fragile mind until only an empty shell remained. Sadly, he lost the plot, never to regain it.