When Dumbledore was duelling Grindlewald, he didn't want to defeat his ex-best friend, but then he thought of Ariana...

Regulus wasn't going to meddle in the Dark Lord's business por finding the horcrux, but then he thought of what Sirius would have done...

Colin Creevey was going on his way back through the tunnel to the Hog's Head, but then he thought of how Harry would praise him if he fought...

tonks wasn't going off to find Remus por leaving behind her child, but then Teddy's hair turned the exact same colour as Remus'...

Narcissa was prepared to tell the Dark Lord that Harry was alive, but then she thought of her son, and decided her loyalty was not as important as him...

Neville wasn't going to say anything when Voldemort came back with Harry's body, but then he thought of his parents, and how he was never going to be called a loser por anyone again...

Snape was going to kill Harry when he noticed Lily's dead body in Godric's Hollow, but then he saw Harry's eyes...

And finally...

Harry wasn't ready to walk into Death's hands, but then he thought of Ginny, of Hermione, of Ron, and of the people who had died for him (his parents, Cedric, Sirius, Dumbledore, Remus, Tonks, Fred, and the bravest of all: Snape)...