The Rebbe encourages a Chassid not to lose heart from difficulties, as ups and downs are part of Jewish and Chassidic life. He urges him to continue fulfilling his mission of spreading Chassidus with strength, assuring that this will lead to true success and blessings in both spiritual and material life.
https://www.torahrecordings.com/rebbe/004_igros_kodesh/iyar/998