Shaarei Teshuvah שערי תשובה

The book takes repentance apart into its elements: regret, abandoning the sin, confession aloud, resolve for the future—and lists twenty "beginnings" of repentance, from anxiety to acceptance. The third gate is a list of prohibitions by gravity, from the lightest to the heaviest, and in that list evil speech stands higher than is commonly supposed.

Rabbeinu Yonah was among those who in their youth opposed the books of the Rambam, and later, by tradition, repented of it and vowed to teach in his memory. So a book on repentance came to be written by a man who knew the subject from one particular side.