Harry Potter struggled a lot to figure out how to cope with everything that happened to him and those around him and he still, arguably, couldn’t get over everything that happened.
When it comes to Harry Potter, he isn’t exactly the happiest. No matter how hard he tries to escape his past, he always goes back to the things he’s done and worries about what happened to his parents and what will happen to his family. Which is very noble of him.
What sucks for Harry is that even when he’s seemingly happy, when he has a family and is functioning outside of what he’s known, he’s still bogged down by Voldemort and what happened to him. Look at Harry Potter and the Cursed Child. Harry isn’t okay with what happened with Cedric even years later and that weighs on him in ways that we, as the audience, didn’t realize.
Cedric Diggory still has his blood on Harry’s hand, in Harry’s mind, and if he feels that way about Cedric just imagine how he feels about everyone else. Cedric was just one of the first people he lost that wasn’t James and Lily. Imagine how Harry feels about Fred and Lupin, Sirius and Dumbledore. All these people died because of Voldemort and if Harry blames himself for Cedric, he probably does the same with them.
It’s sad and unfair. He worked so hard to live the best life but even in Cursed Child, we can see he still struggles to find that balance from his past.