The book HaYom Yom, from Day to Day, has daily sayings by the 6th chassidic leader, or rebbe (aka grand rabbi) of the Lubavitcher hassidim (as organized by the 7th rebbe).

For Tuesday, 27 Adar I which is equivalent to the english date March 8, the Rebbe writes about a saying of his father, the 5th chassidic leader of Lubavitcher hassidim...

My father said: Truth is the middle path. An inclination to the right, to be overly stringent with oneself and find faults or sins not in accord with the truth, or an inclination to the left, to be overly indulgent, covering one's faults or being lenient in demands of Avoda [service to G-d] out of self-love - both these ways are false.