A few things which I believe are important. Whereever you keep your gun at night, make sure there is a cell phone near it...even if it's an old cell phone. Every cell phone must be able to call 911, even those not in contract.
Get yourself an alarm system. It does two things...it wakes you up and lets anyone who may be intruding that the police are on the way. Being awakened by an alarm instead of a bump in the night is certainly a better start to a bad scenario. Then there are dogs, deadbolts, motion detectors...etc...a whole array of things that can be done to help you prevent a bad situation. At the very least, have a safe room you can go to, with a phone and have a plan in place with your girlfriend for those "just in case" moments. Situational awareness means everything, before and after something happens.