Quitting smoking after two years?

Im twenty years old and have been smoking since I was eighteen. Im in overall good health despite my bad smoking habit. I made it through the fire academy at nineteen and im now currently an EMT. I feel bad because I smoke and a lot of the calls we get are cardiac and respiratory arrest and heart attacks. I need to quit smoking for the sake of my life so i can continue helping others. I know a few ways to quit and I know I can google and figure out some of the best ways to quit smoking but this seems relatively easier with all the different potiental answers. It is fairly difficult for me to quit I've been off and on for the last six months but it never seems to just go away. Everytime I have a bad call I just light one up and that's all she wrote for about a month or so. Im curious to see how you guys quit.