Well, being a paramedic I have had occasion to save a few lives here and there, but that is just how this work goes.
The differences I remember is the look on a patients faces. You arrive and they are unable to speak because of their condition. Asthma, CHF, COPD, and a few others are the biggies. They look at you and you can tell by their eyes that they are very scared, and are pleading for you to help them, all without speaking a word. You work very fast on those calls. Whether it is some breathing treatments, insertion of a breathing tube, IV meds, or a combination of all of those, they get better before your eyes. It is a great feeling when they grab your hand and give it a squeeze to let you know how much they appreciate your help.
There is no better feeling for me.