Tess Gerritson makes some interesting comments about this topic:
Even in stories for younger audiences where killing is not part of the plot–bad things can and do happen to the protagonist. If everything goes along smoothly–where’s the story? The character arc is developed through the telling of events (both good and bad) and by showing how the characters react.
Think of this story:
The story would definitely not be the same if Alexander’s day went smoothly. Of course, Viorst shows the reader how important perception and attitude are, as well.