The Rebbe provides two essential guides: First, success in Torah study is guaranteed through effort ("Yagata u'Matzata"), but is enhanced by daily Tzedakah and the study of Chitas. Second, to maintain joy and avoid sadness, one should study the end of Hilchos Lulav in Rambam and the specific chapters on this topic in the Tanya.
https://www.torahrecordings.com/rebbe/igroskodesh/016/005/6033