It’s possible that the most important part of Harry Potter, the entirety of the series, is in PoA when Harry realizes that no one is coming to save him, that it wasn’t his father he saw casting the patronus and sending the dementors away. When he realizes that he has to save himself and he does it.
Also, considering how the Dementors represent Depression, I think the message here is very powerful and real. No one can save you from it but yourself.