What you are waiting with , if you are eager to see someone, or to see something happen. Unlike holding my breath, which is often in vain, waiting with bated breath generally ends up with a satisfactory conclusion-the event waited for occurs.

Often used interchangeably with breathless with anticipation.

It is a little interesting that so many expressions about patience and waiting involve loss of breath or breathlessness. Is it that hard for us to wait without panting?

thanks to wharfinger for some much needed grammatical assistance.