Why do paramedic need to have a positive attitude?

A nurse does not NEED to be optimistic but if they are nice then it could make the patient's happier, and help them recover faster; it could also help the nurse coope with the bad situations they might face. I think a good nurse also needs to be empathetic and understand where the patient is coming from. I mean, would you want to be in a hospital bed and feeling sick and then have a mean nurse yell at you all the time? No way!