I think the two things the youth fears are the possibility that he will not be able to conduct himself honorably under battle conditions, and  the feeling that he is the only one that feels this way. 

The youth has "doubts which he privately acknowledge(s) in himself", and he expresses them in asking the loud soldier, "How do you know you won't run when the time comes?"  The soldier's comparatively confident response does not reassure the youth, and "his failure to discover any mite of resemblance in (his comrades') viewpoints (make) him more miserable than before...he (is) a mental outcast".  The youth is afraid of how he will react under battle conditions, and he is also afraid he is alone in his fears.

A good example of personification in Chapter 2 can be found in the eleventh paragraph.  The author is describing what the youth can see in the early morning, and gives human characteristics to both the fires of the opposing army and the rising sun.  He says, "from across the river the red eyes were still peering" in referring to the campfires, and describes the first daylight as "a yellow patch like a rug laid for the feet of the coming sun".