A tzaddik who isolates himself and escapes the world ceases, at that moment, to fulfill his duty as a tzaddik.
The tzaddik's mission in life, his duty to his fellow man and to God, is to involve himself with the world and elevate it.
The story is told of a tzaddik who once fell ill and sent a request for a blessing to one of the leading Hasidic rebbes of the time.
In response, the rebbe instructed him to eat a large meal of milk products in order to be cured.
The rebbe subsequently explained that this tzaddik never ate cheese, and it was the cheese's accusation against the tzaddik, that he had neglected to elevate it to holiness, that led to his illness.
His cure would therefore be to eat cheese, so that the accusation would be withdrawn.
–Rabbi Adin Steinsaltz
From Opening the Tanya, p. 266, by Rabbi Adin Steinsaltz