Perek 4

4:6

Someone who studies something and takes the time to understand it will not forget it quickly. However, someone who tries to learn many things superficially will not understand any of them and quickly forget them. Superficial study does not remain with a person and will quickly fly away. The same is certainly true when it comes to Mitzvah performance. It is preferable to so one Mitzvah properly with understanding of the purpose of the Mitzvah than to do many in a haphazard manner without any Kavanah.

4:15

Even though Tzaddikim are generally under the control of their Yetzer HaTov (good inclination) they occasionally are influenced to do evil as well. Don't think that this is only true of modern-day Tzaddikim who are two weak to fight their impulses, but the ones in earlier generations did not sin at all, because this is simply untrue. We see that Noach who was a Tzaddik planted a vineyard and got drunk and created a situation that caused himself embarrassment. Yaakov acted in a deceitful manner. Moshe became angry. And if the great ones could err, surely the lesser Tzaddikim cannot completely remove themselves from the influence of the Yetzer Hora.