"But, Harry," Gellert tried to assure him on this matter that he and Albus agreed on so deeply, "the things we do are done because of who we are. They aren't just a reflection of that. They are a manifestation of our character."
Grindelwald gulped and rubbed his forehead. This wasn't the first time he would be asked these questions. And even if he didn't answer them, he had to get used to them being asked.
He had always believed in serving the greater good, even when his ideas of how to do that were warped. And now, the greater good was served by having tea.
And it's incredible tea! So he sat down and raised the cup to his lips again.
"Every hour is a struggle," he said in answering the question. "A struggle to overcome more guilt than you could feel in a thousand life times. Despite all the evil I've done in the past that I have a chance to do some good, and doing that good -- whether it's as small as throwing a birthday party for a house elf or as large as helping you solve this Riddle -- will do more in showing the world that I regret my actions than any number of apologies or years in prison."