I think that Perpich is trying to mean that his body is the best thing to help him to survive, which means he will have to use his body to survive in the forest. He has to use his body to make things too, but he can also use his body parts to eat, I mean, if necessary.

One thing that Brian can do is think positive, because if he thinks negative his heart will beat faster and faster, which can give him a heart attack, but if he thinks positive, his heart will beat normally.

He can use the rest of the gas in the airplane to make fire.

He can use his hatchet to kill animals and eat them, or maybe even make clothes with their skin.

He can make a house on a tree to survive among the night.