At this point, Mark doesn't think anyone will even realize that he survived, much less rescue him. This creates a sense of isolation that's both figurative and literal: he's afraid of not only being abandoned but forgotten. Luckily, this pessimistic perspective is quickly squashed by his seemingly limitless supply of optimism.

We don't know if we'd be quite as graceful if we were in Mark's situation—frankly, we'd be cursing those rapscallions to high heaven. Still, you've got to admire the guy. Instead of getting bitter, Mark realizes that he sacrificed himself so his friends could live.