What I got from the book "Deep Survival" is that you really can't know for sure. It's more of a mental attitude thing than anything, and there's no way to know what you've got until you need it. I've heard of a survival instructor with everything basically just giving up and dying. One the other hand, a 14 year old girl with nothing walked out of the Amazon jungle from a plane crash, carrying nothing. What's most important is the will and determination to survive. What we carry with us just gives that will and determination something to work with.