Step 1) Learn the tricks used by a locksmith (last time I called one he opened my door in about a minute with a piece of cardboard). Step 2) Install self-closing lock thing Step 3)Never go out without a piece of cardboard ;)

(I recently came home from work after midnight to find one of my friends waiting for me *inside* my flat---he'd got cold waiting for me after about an hour, wasn't able to contact me because I'd disconnected the net connection, found a phonecard and opened the door with it)