Idiom for people complaining excessively

What is an idiom applicable when someone is voluntarily participating in an action, and complaining excessively? I thought of using "don't let the door hit you on the way out", but I don't want to tell the person to leave, just want to say something along the lines of "nobody is holding you here"?

If you can't stand the heat, get out of the kitchen.
Phrasefinder

Don't persist with a task if the pressure of it is too much for you. The implication being that, if you can't cope, you should leave the work to someone who can.

But sometimes a person, especially one who never seems to be satisfied, deserves a sarcastic epithet.

You're a right ray of sunshine.
You're a bundle of joy, this morning. Aren't you?
Don't tell me. You must be the glass is half full kind of person.

If the person still doesn't get it, just tell him or her straight:

Has anyone ever told you: "You're a miserable so and so"?
Can you stop acting like a crybaby for once?
Could you keep your whinging to yourself?