Thats a very good question and even though I am no expert, I will take a crack at it. There are countless things that could cause a SHTF scenario. A virus that sweeps through the world and kills billions, a major meteor strike, nuclear holocaust, major volcano eruptions etc. etc. etc...... If you survived, that means that possibly millions of others have also survived. Unless you are out in the middle of nowhere, it would be difficult to survive on your own. There will be people banding together all over the world to survive as groups. Being alone and by yourself would be difficult to defend yourself and yours against these other groups of people. I don't think you can assume, if you stay in your basement long enough, that everyone else will die or kill each other. People who are not survivalists (as being discussed here) will survive, even if it takes killing and taking from those who are weaker.