Tanya for the 28th of Cheshvan כ''ח מר חשון

One proper prayer, or even a compilation of different prayers that add up to one prayer with proper intent, elevates all the other prayers of that year. With regard to Torah study, by contrast, even if one later studies with proper intent, this does not elevate his previous study; actual repentance is required. Until such time, one’s Torah study is in exile within the kelipah which spawned his ulterior motive.