Musar do Joela 2:13

When sufferings of chastisement come upon a person, he returns to the good. As the sages interpreted the Song of Songs, "Behold, you are beautiful, my beloved, and pleasant" - even when You bring upon me sufferings of chastisement, it is pleasant. Why? Because You return me thus to the good. Human repentance is never complete without suffering. Repentance is improving one's actions and character. It is not fasting and wearing sackcloth and wallowing in the dust and immersing in water while remaining soiled on the inside with sins and evil thoughts. And so said the prophet (Isaiah 58): "Do you call that a fast, A day when the LORD is favorable?" "No, this is the fast I desire: To unlock fetters of wickedness, And untie the cords of the yoke." [...] The intent of the Torah is that one should first cleanse oneself on the inside, casting out from one's heart the impurities of sin, and then return what one has taken unfairly or by violence, and ask forgiveness from one's friend. After immersing one's heart inwardly and doing all kinds of purification and cleansing oneself from sin, one should purify oneself also outwardly by fasting and immersing the body, and so on...

Finally, he should know how to strengthen himself exceedingly and to bear the great burden of restraining himself from that evil which he is accustomed to do. For this is obvious that a sin that he has been accustomed to do all his life he will regard as permissible (Yoma 86b), and it is very difficult for him to give it up. Therefore, a man needs great will power and high fences to give up what he has been accustomed to. And it requires a great accord in all his heart and soul to hold himself back from committing that sin, and he must remove this habit from his heart as though he had not been accustomed to do this. And he must become accustomed to reject in his heart all the evil things, as it is said, "And rend your heart and not your garments" (Joel 2:13). And when the sinner establishes these seven considerations firmly in his heart, he is very near to the path of repentance.

I have explained repeatedly that there are two kinds of repentance. The first is occasioned by the sinner experiencing various forms of afflictions at the hand of G–d; their purpose is to get him to remedy his mistakes and change his life-style. This may be considered an externally induced repentance. The second, which we will call internally induced, originates in the heart. The prophet Joel 2,13 calls on Israel: "Rend your hearts rather than your garments; turn back to the Lord your G–d. For He is gracious and compassionate, etc." When the heart is sincere such repentance is viewed as emanating from love for G–d, meaning that one feels remorse that one has rebelled against the King of Kings. It is not merely due to fear of punishment.