When Rav Hutner was a young man he learned by himself without a chavrusa. His Rebbi, the Alter of Slabodka, asked him why he doesn't learn with a chavrusa. He replied "I learn with my yetzer hara." The Alter asked him why he doesn't learn with his yetzer tov?
He replied "My yetzer hara is always there and also he has a better head."