4151b - This is not the way to make up for the past by fasting to do Teshuvah.

As the Alter Rebbe writes, nowadays fasting can, God forbid, bring health issues. Study more Torah, daven properly with a minyan, and say Tehilim. Study Chitas. Do as the Rebbe Maharash said: take 15 minutes to think about your situation to bring about an addition to your Torah and mitzvot. https://www.torahrecordings.com/rebbe/igroskodesh/012/006/4151b