Why are nurses so mean?

Nursing........... most nurses are pressed for time.......stressed with trying to give correct meds and procedures...........after time nurses get stressed out and pissed off. After working in a hospital for a little over a year I found myself getting annoyed more easily than usually.......why? Is it the patients??? Hitting the bell every five minutes for no reason??? Or is it the nurses we work with??? Getting pissy and critical of your every move???? Perhaps it is the environment itself?? Maybe it is a combo of all those three?? Getting annoyed more quickly can be because of the patients and because of the bitchy nurses around us...... The question still remains....... why are nurses so mean?