Voldemort seemed to see Harry's confusion and chuckled softly. "There were things my former self could not sense, but looking back now, I can see some clues. Some of the measures I took to avoid death worked, but they inevitably produced a few side effects.
As he spoke, Voldemort tapped his head with his long fingers. "They made me mentally unstable. My previous understanding of the soul seems to have been somewhat one-sided. Fortunately, fate still favored me. Wormtail brought me an interesting little piece of news: an interesting little spell could actually strengthen the soul."
By this point, Harry's expression had changed. He knew what Voldemort was talking about.
Sure enough, Voldemort continued, "I know Occlumency, and I have practiced it consistently for many years. But it is more functional than beneficial. It helps the soul, but not that noticeably. Wormtail, however, brought me a new-or perhaps I should say ancient? In any case, an interesting little spell. Though slow, it can strengthen the soul.
"It was precisely through practicing this ancient magic that I discovered how foolish the things I had done before were. Fortunately, it seems there is still time to make amends. Thank you, Wormtail."
"My honor, great master?" Peter bowed deeply.
"And thank you, Potter." Voldemort looked at Harry again. "It was you who taught this spell to your good friend, young Ron Weasley, allowing Wormtail to learn of it. Though he was too stupid even to master it, he allowed me to benefit from it."
Just as I thought.
Harry's expression darkened. Voldemort was talking about the Meditation Technique.
In his first year, he had written the key points of the Meditation Technique on a deliberately aged piece of paper and taught it to Ron, Hermione, and Neville. All three had been very principled