Did Dumbledore ever fall in love again? Or was the whole mess with Grindelwald so traumatizing that he guarded his heart carefully against ever falling in love again? How devastating it must have been, to see the one he loved hurt his family, and turn into something so dark and twisted. To reconcile himself with the fact that he had loved a monster. How horrible it must have been to finally confront Grindelwald, knowing that it could end by him killing someone he loved, or by the one he loved killing him.
But, maybe he didn't care about the possibility of dying by Grindelwald's hand. Maybe he would have considered that a mercy, that he deserved to die because he failed to protect Ariana (or possibly killed her). And maybe he thought that if he did succeed against Grindelwald, if he did kill him, it might make up for what happened to Ariana, and of course save countless other lives. So he finally drove up the courage to fight someone he loved to the death.
But, I think, in the end, Dumbledore found that no matter how horrible Grindelwald had become, he couldn't let go of that love, he couldn't bring himself to kill him. And instead he won the duel without killing Grindelwald, leaving his former love and friend to a life of imprisonment. But I bet he felt guilty, guilty that he had shown mercy, guilty that he still cared enough to keep Grindelwald alive. So incredibly guilty that he had loved, and might always in some way continue to love, a monster.
And maybe he felt that if he could love a monster, maybe it was best if he never loved again, if he never grew close to another again. Maybe this was another reason Dumbledore struggled so hard against how he was growing to care for Harry, as a father figure Harry so desperately needed. Dumbledore was often so distant and cryptic around everyone, refusing to elaborate further on his plans than necessary, because he was resisting letting anyone in. Because he was used to shutting people out as he took care never to risk his heart again, not just romantically, but platonic-ally, familial-y.
He was afraid to love again. He was afraid of getting hurt again. Afraid of loving a monster again. Afraid that maybe his love corrupted others, destroyed them.
We know that Dumbledore did care for Harry, maybe thought of him as a son. But, this love was damaged by Dumbledore’s past and the situation surrounding Harry and Voldemort.
Dumbledore always knew Harry was going to die. And until Voldemort resurrected himself using Harry’s blood, Dumbledore wasn’t even sure if he could save the boy. And once he had found a way to save Harry, he wasn’t sure if it would work. And so he tried not to care about Harry, knowing that he was leading him to his death.
Because he wanted to save the world from Voldemort, but it came at the cost of a boy, and if he grew to care for Harry, then he might lose his nerve. So he was both unconsciously and consciously trying not to care for Harry. But, he failed. He did care for Harry. Harry was someone that broke through to Dumbledore’s broken heart and taught him to care for someone again (as a father figure). But by the time Dumbledore began to love again, his heart was too fractured and damaged to love purely. He was still afraid.
And so Dumbledore kept Harry in the dark and lied to him and manipulated him, attempting to protect him and keep him at arm’s length. He wanted to protect Harry from himself and protect himself from caring for Harry. The result was that Harry never ended up knowing much of anything about Dumbledore until after his death. And that Harry was completely lost and confused for much of Deathly Hallows, angry that Dumbledore had never trusted him.
It just goes to show how much love can damage people, the effects rippling into the lives of so many. If Harry’s life shows the benefits of love, then Dumbledore’s life shows the consequences of it.
