Four Rules of Three

The main point of the Rules of Three is that we need to concentrate on the most immediate problem first. People mainly think of these rules for being stranded in the wilderness, but they also apply in an urban setting, such as natural disaster, earthquake, flood, etc. In any extreme situation:

You can survive for 3 minutes without air (oxygen) or in icy water,
You can survive for 3 hours without shelter in a harsh environment (unless in icy water),
You can survive for 3 days without water (if sheltered from a harsh environment),
You can survive for 3 weeks without food (if you have water and shelter).

Some people have suggested a fifth rule and that is 3 months without hope.

Incidentally, if you have a stick, or knife, or any other object stuck in you, do not pull it out. The object restricts blood flow. Wrap the area around the wound and seek help as soon as possible.