A couple of reviewers have noted that Johan seems to verge between near adulthood and an immaturity more common to a twelve-year-old than a seventeen-year-old (never mind that some seventeen-year-olds can be quite immature, I know I was). Among other things, he loses track of what he can do, he doesn’t seem to see obvious solutions to his problems (although one of the solutions the reviewer mentioned isn’t actually possible) and he has problems controlling his emotions. This isn’t an inaccurate diagnostic, really.
Unfortunately, Johan’s mental state has been quite badly warped by his life prior to the story.
Johan grew up without magic in a family where magic is everything. From their point of view, he’s a cripple (at best) and a dread embarrassment (at worst). His mere existence calls into question the magic running through their veins. Think of him as a kid who is so severely disabled that he has no hope of living a normal life.
So Johan spent the first 16 years of his life trapped between two separate (but both bad) attitudes. One attitude sees him as permanently helpless, someone who literally cannot do anything for himself, the other sees him as a useless piece of s***. Basically, he spent most of his life facing well-meaning condescension or endless, merciless, bullying.
Making this worse was the simple fact that he probably could have created a pretty good life for himself, if he was allowed to leave the family permanently. There are plenty of positions for non-magicians within the empire. But his father refused to allow it, both out of the conviction that Johan literally couldn’t make anything of himself and out of fear that Johan, who was defenceless, would be captured and turned into a weapon aimed at the family.
So, by the time of the story, Johan is trapped in his own mind, trying to maintain some independence against a family of people who might as well be gods. (Imagine you were the powerless third son of Clark Kent and Lois Lane?) Of course he has problems coming to terms with the power he suddenly acquires, let alone seeing possible solutions to his problems. You’d have problems too. <grin>