What does 'walking pins and needles' mean?

Answer 1

This is actually a good example of mixing your metaphors. When you mix a metaphor it means you are combining two different idioms. Walking on egg shells means you are trying very hard not to offend or bring attention to yourself. To be "on pins and needles" means you are anxious about something usually anticipating some bad news. To walk on pins and needles is not an idiom that is often heard or used unless you want to describe how you are trying to avoid attention while waiting for possibly bad news. Mixing metaphors is not uncommon but it's usually done to be funny.

"When my mother-in-law comes to visit I am always walking on egg shells". "I'm always on pins and needles waiting for my final grades".