no like really this time i am actually and legitimately ashamed of myself

You don’t understand. I — I made a grave mistake in marrying Tonks. I did it against my better judgment and I have regretted it very much ever since. Don’t you understand what I’ve done to my wife and my unborn child? I should never have married her, I’ve made her an outcast! You have only ever seen me amongst the Order, or under Dumbledore’s protection at Hogwarts! You don’t know how most of the Wizarding world sees creatures like me! When they know of my affliction, they can barely talk to me! Don’t you see what I’ve done? Even her own family is disgusted by our marriage, what parents want their only daughter to marry a werewolf? And the child — the child — my kind don’t usually breed! It will be like me! I am convinced of it — how can I forgive myself, when I knowingly risked passing on my own condition to an innocent child? And if, by some miracle, it is not like me, then it will be better off, a hundred times so, without a father of whom it must always be ashamed!
— 

Remus Lupin, Deathly Hallows

I honestly think that this is one of the single best pieces of dialogue that Remus has ever given us. This is so insightful, and it’s a really nice window into the real Remus that nobody ever gets to see. He’s not the teacher Harry is accustomed to anymore: he’s been stripped down into something smaller than all of his disguises, to bare his raw feelings on his sleeve such that it becomes clear that Remus is breaking down.

“I did it against my better judgment and I have regretted it very much ever since.”

This is a lie, but not exactly without truth. Remus loves Tonks. He loves her so much that it actually scares him, because he’s never let himself love someone else before. But he’s also scared because he feels that he’s ruined her life by becoming her husband, and he loves her–which means that even though he does care for her, he has hurt her simply by loving her back. Remus is afraid of himself and his affliction, and even though he does everything in his power and then some to make sure Tonks is not directly affected by it in any way (aside from helping care for Remus) he is convinced that just through power of association that he has ruined Tonks’ life. He feels that he is toxic to others by sheer presence alone. He doesn’t regret marrying Tonks because he doesn’t love her, he regrets marrying Tonks because he thinks that in doing so he has permanently scarred her, hurt her. His arguments for not being in a relationship with her are not personality based. They aren’t even about her. They’re about him, about what he offers Tonks as a man.

“I am too old for you, too poor….too dangerous….”

That little pause between the words is actually a huge giveaway. Yes, sure, he’s much older than Tonks, he hasn’t got a lot of money to provide for her, but he is also very dangerous and the fact that that was the last thing he said (particularly after hesitating) means that it is the most important thing on his mind.

“You have only ever seen me amongst the Order, or under Dumbledore’s protection at Hogwarts! You don’t know how most of the Wizarding world sees creatures like me!”

This is–sad. Actually, legitimately sad. “Creatures like me.” Remus doesn’t even consider himself human. He believes that he is second class or lower, unworthy. He believes that he is tainted, and that even though his body is human and his mind is human that because he suffers from this disease that he is no longer a human, no longer a person. Remus sees himself as a creature–something subhuman, and indeed something wild and dangerous. He believes that the Order treats him with respect because he is under protection from Dumbledore, but is clearly suspicious that they would not feel the same without the Order binding them all together through necessity. He suspects that they harbor misgivings about him because he’s a werewolf–and why not, when that is exactly the sort of thing that made even his own best friend turn on him in the First War? He’s suggesting that even Harry might think of him differently if he had been raised like the rest of the Wizarding world, and that people like him and James are a fluke of nature who go against everything the rest of the world believes about werewolves, and he’s probably right. (Arguably Harry would change his mind, just as Ron did, but if he had been raised by, say, the Weasleys or another wizarding family he would share the commonly held beliefs in wizard society just like Ron did.)

“Even her own family is disgusted by our marriage, what parents want their only daughter to marry a werewolf?”

I wish we knew more about whether this was true, because Andromeda Tonks was no typical witch. She married out of the Black family and rejected their pureblood mania before having Tonks with the Muggle-born Ted Tonks. She was burned off the Black family tree. I think if anyone could support an unusual marriage in the name of love, it would be Andromeda. And Ted? Remus’ child is named after him. I don’t think a poor relationship fosters such an act. Truthfully, I think this is Remus digging deep into his own fears and loosing track of what’s real. His anxiety is so out of control that he’s essentially lied to himself about what is actually happening. In his mind, how can they not hate him? They must hate him. They have to hate him. He can’t fathom it. Any dislike Tonks’ parents may have of him is automatically, to Remus, the result of him being a werewolf. And this compounds his anxiety immensely.

And the child — the child — my kind don’t usually breed!

Again, more of Remus dehumanizing himself. Remus doesn’t say “my people,” or “werewolves don’t usually”, he says “my kind.” His species. And he uses the term “breed”, which sounds primal. Humans don’t “breed,” they give birth. They procreate. Animals breed.

“-how can I forgive myself, when I knowingly risked passing on my own condition to an innocent child?”

Remus is going back to his own childhood, to his own ingrained feelings about Fenrir Greyback. He’s comparing himself having a baby with his wife to the savage act of purposely infecting a 4-year-old child over a put down. He’s essentially saying that once he agreed to consummate his marriage, to make love with his wife, that he became no better than Greyback because he knew he could infect an innocent person and chose to go ahead anyway. Remember, up until Teddy Lupin was born, nobody knew whether lycanthropy could be transmitted through childbirth because Teddy Lupin is actually unprecedented. So Remus is heading into completely new territory with his condition as well as facing his internal guilt at what he thinks must automatically be the outcome.

And if, by some miracle, it is not like me, then it will be better off, a hundred times so, without a father of whom it must always be ashamed!

“If, by some miracle, my child is spared being a werewolf, he’s going to be much better off without me in his life because I am nothing but a source of shame who will ruin his entire life from the very start just by being his father.” Remus is really laying on the self-loathing thick here. This isn’t about his worries anymore, this is him slamming on himself and digging the knife further into his chest because he thinks he deserves it. Remus can’t hide the fact that he loathes what he is in private conversation–it just comes out with his tone. But this is him outright proclaiming to be the monster everyone has always told him he is, because no matter the kind of person Remus may be he is still a werewolf and still as unworthy to raise a child as the monsters he knows all too well. Remus would rather not be in the life of his child at all because he thinks that, just like Tonks, the only thing he can offer it is pain and hurt, and he loves it–and Tonks– too much to burden them with what he is.

And so he goes to Harry, seeking to join him on what is effectively a likely suicide mission to deal with the Horcruxes. He wants to disappear, and if he dies in battle at least he will have died heroically and perhaps that will minimize Tonks’ hurt at having lost him: her husband was a hero, at least he was that.

Remus is ultimately thankful that Harry yells at him, because it gave him the shock enough to be able to take a step back and realize how far he was deluding himself and how wrong he was. He saw that rather than being the brave man and suffering for his family, he was abandoning them. And Remus proved his Gryffindor nature by plucking the courage to go back to a very pregnant Tonks and demand the forgiveness of an incredibly powerful auror. And more than that, he found the courage to be a father and raise his family even knowing the risks. Even if it turned out to be groundless, the act of facing his fears is remarkable. And this little piece of the Deathly Hallows is perhaps my favorite for that reason.