Chapter 15 (end), 18, 19, 25. Third category of Beinoni: Working with “Ahava Misuteres”; hidden love for G-D hidden in the soul of every Yid. Harnessing that power (of self sacrifice) for one’s regular service of Hashem.
Note: Lessons 17-23 explain the (Ahava Misuteres) Soul based (rather then the mind over heart) Beinoni.