Priorities

The survival rule of threes:

It takes about three seconds to die without thinking
It takes about three minutes to die without air
It takes about three hours to die without shelter
It takes about three days to die without water
It takes about three weeks to die without food
It takes about three months to die without hope
Try to have at least three ways of preventing each of the above (a backup to your backup).

So the priorities are thinking, air, shelter, water, food, and hope. These are rules of thumb and approximations. Also, you will likely start feeling really bad before you die so you need to be proactive in addressing these needs.