In Hatchet, why didn't Brian light the signal fire right away?

Brian did not have enough wood to keep the signal fire going constantly. Also, he needed to be able to go out and search for food, which he couldn't do if he was constantly babysitting the signal fire and gathering wood for it. He decided to have it ready to go, but only light it if he heard a plane coming.
Unfortunately, when a plane does come, Brian happens to be far away from his campsite. By the time the runs back and gets the signal fire lit, the plane has already passed.
This heartbreaking disappointment marks a turning point for Brian. Instead of expecting to be rescued soon, he gives up on the idea of rescue. He figures he will have to survive on his own in the wilderness, perhaps forever. His excitement at seeing the plane, and his disappointment, are so intense, and the mental shift he must go through is so great, that he thinks of himself as having become a different person after this incident.