How can i get over the fear that someone will screw up during my surgery?

well, i have a birthmark right above my lip that i want to get removed. but the doctor said it has pigment in it so i cant get it removed with a laser. basically they are gonna numb my lip, cut it out, and stitch it up. they also said it wont take more than 15 min. pretty simple, right? well, im terrified that they are somehow going to mess up. like, they will cut more than the birthmark. one wrong move can mess everything up. or they wont give me enough medicine to completely numb it, and i will feel it. and the fact that i will be awake scares me even more, like i will suddenly move or something and they will cut more. anyway, i really want to get my birthmark removed, but how can i get over this fear??