Answer:
I think the answer is "Writing can be a powerful experience to work through struggles"
Step-by-step explanation:
All his examples seem to be depictions of being able to digest something that was easy for him to comprehend, but his one memory that sticks with him is one that had a impact on him, and his emotions in a way he couldn't seem to figure out. With his statement of "Writing is useful at these times" makes me think that he wished he had some form of outlet to confess confusing thoughts/feelings too.
This is just my interpretation, and what I think the teacher might be looking for. I hope this helps, I'm really sorry if it doesn't . Good Luck!