How we cite our quotes:
I got bodily into the apple barrel, and found there was scarce an apple left; but sitting down there in the dark, what with the sound of the waters and the rocking movement of the ship, I had either fallen asleep or was on the point of doing so when a heavy man sat down with rather a clash close by. The barrel shook as he leaned his shoulders against it, and I was just about to jump up when the man began to speak. It was Silver's voice, and before I had heard a dozen words, I would not have shown myself for all the world, but lay there, trembling and listening, in the extreme of fear and curiosity, for from these dozen words I understood that the lives of all the honest men aboard depended upon me alone. (10.30)
It sounds like Jim is feeling a rush about the fact that "the lives of all the honest men aboard depended on [him] alone." Suddenly, he's going from cabin boy, the lowliest member of the crew, to the savior of all. One reason Jim always finds himself in the right place at the right time is because he's so young. He's small and childlike enough to climb right into an apple barrel and fall asleep, which sounds like something we would have done when we were kids. Jim childlike nature is the very thing that saves the "honest men" on board the Hispaniola (or at least, many of them) from death at the hands of the pirates.
I began to recall what I had heard of cannibals. I was within an ace of calling for help. But the mere fact that he was a man, however wild, had somewhat reassured me, and my fear of Silver began to revive in proportion. I stood still, therefore, and cast about for some method of escape; and as I was so thinking, the recollection of my pistol flashed into my mind. As soon as I remembered I was not defenceless, courage glowed again in my heart and I set my face resolutely for this man of the island and walked briskly towards him. (15.4)
Jim is recalling tall tales and freaking himself out as he sees the then unknown Ben Gunn in the distance. But he suddenly remembers that he's not "defenceless" – he is armed – and he takes confidence. We can contrast Jim's ability to overcome his fear with the cowardice of the pirates, who believe the forests are haunted in the later chapters of the novel. Jim is slowly becoming more mature than full-grown men like Tom Morgan and George Merry. Something about pirate life seems to keep them from maturing. For all of their violence and toughness, they still seem like self-indulgent and easily frightened children.
As for the scheme I had in my head, it was not a bad one in itself. I was to go down the sandy spit that divides the anchorage on the east from the open sea, find the white rock I had observed last evening, and ascertain whether it was there or not that Ben Gunn had hidden his boat, a thing quite worth doing, as I still believe. But as I was certain I should not be allowed to leave the enclosure, my only plan was to take French leave and slip out when nobody was watching, and that was so bad a way of doing it as made the thing itself wrong. But I was only a boy, and I had made my mind up. (22.15)
There is only one other moment in the book we can think of when Jim tries to justify his actions – in a scene we discuss in the "Quotes: Friendship." He must feel that leaving his friends behind with no warning was the worst thing he did, because this is the one act he explains away as that of "a boy." Do you buy the explanation that Jim sneaks off because he is "only a boy"? Does it matter to you why he leaves his friends? By the way, taking "French leave" means abandoning your post without permission – a slur on French sailors, as you can imagine.