That holds true for most people, but sometimes you are dragged into something you don't want to. For example, if you are minding your own business running a convenience store and some guys come in with guns demanding money, and out of fear for your life, you shoot first and kill one of them. Now you have to spend the rest of your life in jail for something that you never premeditated or wanted to have happen.
Interesting how you define premeditation, is it only premeditated if the whole scenario was planned? One could argue, that by purchasing and carrying a firearm you had already decided, ie. premeditated, that in certain circumstances you would use it to shoot someone.
Whether or not shooting someone for self defense is reasonable or not is up for debate, but why would you carry a gun if you had no intent to use it, under any circumstances?