Rav Dovid Chaim Stern is a great Rabbi in Eretz Yisrael. He was the Talmid Muvhak of Rav Chazkel Levenstein.
He taught me something amazing, as I have had a history of difficulty with Machshava.
He taught me a method to memorize Mishnayot that helps clean a person's mind.
Take the first line in a mishna repeat it 10 times them do the same with the next line and after that do it with both lines until you finish the whole Mishna by heart. After that repeat the whole mishna 25 times (the amount of mishnayot you cover is not as important as the repetition) This greatly helps with guarding your eyes and your mind. So powerful.