Can I be ready for absolutely anything?

You can only prepare for the worst & do your best.

Cover yourself & your basic needs. The 3, 3's... The 3, C's... 3 Day Buffer of Food & Water. Keep it light weight.

What do you do once the food & water run out?

You need redundancy. Alternative ways to stay dry, get warm, start a fire, cook food, gather water, filter it & not end up getting a Darwin award.