When you use the expression ‘On Pins and Needles’ you mean that someone is in a
state of anxious suspense.
Example of use: “Todd has been on pins and needles all day, waiting for his wife to have the baby.”
The origin of the phrase ‘on pins and needles’ comes from the early 19th century. The expression began as a literal description of the sharp, uncomfortable feeling one gets when recovering from numbness.