Relevant quote, conversation with a Sorting Hat:

"And you would find loyalty and friendship in Hufflepuff, a camaraderie that you have never had before. You would find that you could rely on others, and that would heal something inside you that is broken."

It seems that something broken was healed at last.

PS: Tangentially related to the Harry's inability to rely on others: chapter 31, chapter 70 (Maybe if there were more heroes, their lives wouldn't be so lonely, or so short.), chapter 93.