Practice what you know and learn what you do not know. Read books about life and about history. Discover how others have responded to adversarial situations, whether in ancient history or as a fictional manifestation of a talented author.
This is an important point. Without these qualities, the will to go on may be compromised. A good example of how feelings and compassion play a role in survival is demonstrated in in Cormac McCormack's "The Road". In the book (there is also a movie), the love between a father and his son is paramount to their ultimate survival.
No one can do it all 24 hours a day for days on end. When and if the time comes, you will need to take time to grieve your losses and also time to rest and recharge your mental and physical batteries.
To do nothing is to die. Sorry to be blunt but making decisions and following through with a plan of action will give you at least a 50/50 chance of survival. Do nothing and you become a target.