Question about Stand your Ground and Duty to Retreat.

Hello all.I just completed my CCW classes in Illinois and plan to apply for my permit in the next few weeks. I am still not clear about the differences between "Using lethal force if necessary" and "retreating if at all able". Illinois is a "Must Retreat" state meaning that you must attempt to get away from an assailant before using lethal force. My concern is, in that split second decision, how will anyone make a solid decision that they can or cannot get away? My take is this. If you are confronted by a belligerent person who is 30 yards away and you have access to a locking door right behind you. That would make sense that you retreat behind that door. If he breaks down that door. Then draw. Am I incorrect? I know most people ANA Lawyer here so I will not take this as legal advice. I just need some clarification. This "Must Retreat" law seems like a good way for a lot of CCW carriers to get themselves killed when they had an ability to defend themselves. via /r/CCW http://ift.tt/2qdr8AP