you still have an option to retreat(something a CCW holder is obligated to do).
I suppose it might depend where you are, but not all places put that requirement on you.
Unless your laws require otherwise, if you have a right to be where you are, you are under no obligation to retreat just because you have a gun, any more than anyone else. Not that its not the prudent thing to do, but it may not be the best thing to do, as you saw with getting shot in the back.
Ive always felt that if youre coming up on or past the other side of 50 in being sure its going to happen, then get to it and be as hard an aggressor as you can. Youre a lot more likely to come out on top. Trying to win by reacting generally doesnt go to well.