While shooting someone either in the front or back should never become enjoyable get it clear in head and heart that you will do what is needed to stop a true threat. Then train and practice in a manner that trains your body to follow the action you have set in mind and heart. That is why we should be shooting targets that have true life like images, with some form of threat shown on them. There are those who say you should have threatening and non-threatening targets both on the range. So you practice and and get use to having GGs in and on the situation.
Shooting someone in the back goes against everything we have been taught our whole life. Unless you have trained your mind to make the choice that you need to shot and then block out the whole target, shoot the spot not the whole image, I see lots of us locking up. I have learned this deer hunting, when you see that buck with the massive set of horns you can not make your shot looking at the horns. You have to put all focus on the small 1 inch spot of hair you are going to place your shot into.
May I suggest most here need to read the OP and really give it some thought not just a moments kneejerk reaction while setting at the keyboard.