The Tzadik, Reb Aharon of Strashela, the great student of the 1st Chabad Rebbe, was known as a very exacting individual. During the time when he was involved with the mentoring of young Chassidim, he would denigrate and chastise them on any minor infraction.
Once, in a private audience that he had with the Rebbe, Rabbi Shneur Zalman, he bemoaned that he has no inner vitality in learning or prayer.
The Rebbe responded:
“The verse (Iyov 34:11) states: “He recompenses man for his deed.” However a man acts, heaven repays him in kind.”
“If a person rebuffs another Jew—even with intent for Heaven and for the person own good—Heaven responds in kind, and doors and gates are shut before him.”
“If a person expresses closeness to another, Heaven shows the individual closeness and all gates of learning and service of G-d are open before him.”
(Iggrot Kodesh, Previous Lubavitcher Rebbe, Vol. 4. Pg. 303.)