Most of us go through life without any sort of real privation ever, those of you who may have reservations about eating certain things will quickly lose them in a few days. The mind and body will surprise you with it's innate will to survive that you may not be aware of at all right now.
Knowledge and experience can help, as can the experiences of others who may have learned over a period of years that they can survive what to most of us is an impossible situation.
Three days without any food, cold and high physical activity can change your outlook fairly quickly.