It is very important for a person to learn at least one maseches or a chapter of mishnayos by heart, as this has many benefits:

He fulfills the simple meaning of the verse, ‘and these things I command you today should be on your heart’, implying they should be learned by heart. Our Sages taught that a person who takes the Torah to heart will not have fear of wars (since war comes from lack of Torah study), nor fear of famine (as it says, ‘if you will walk in my statutes’, meaning diligent study, ‘I will give your rain in its proper time), no thoughts of nonsense, nor thoughts of illicitness or misdeeds, because the Evil Inclination resides only in a heart void of Torah, there it takes permanent residence.