Answer:
Joby is afraid of the imminent battle because he is only 14 years old, and this very battle could cause many people their lives, including those with families. Further more no one knows if they'll live through the battle or not.
Joby is afraid of the imminent battle, so he cries in the middle of the night, unsure of what's to come. He questions his role as the drummer boy and his ability to aid the others in battle.
Joby is afraid of the imminent battle, but he knows he has to push pass all odds in order to effectively support his peers in battle, and to ensure their success.
I hope this is what you were looking for, because I literally just read "The Drummer Boy of Shiloh" just to answer this question.
