Jesus Christ “proclaims as blessed those who mourn, but not those who do so for any human reason, as for the loss of some transitory good, but those who have Christian compunction, mourn their sorrows, and expiate their sins and even those of others.”
As for St John Cassian, he writes: “Therefore, apart from that sorrow which arises for the sake of saving penance, or from the desire of perfection, or the longing for what is to come, all [sadness] must be equally resisted, being worldly and pernicious, and quite excluded from our hearts.”
Thus, it is not a matter of abolishing every form of sadness, but only of the passion of sadness. Here again, putting an end to the passion does not mean putting an end to the function itself, but rather healing it, in order to allow it to recover its natural and normal use and to be exercised once again in healthy fashion.
~Dr Jean-Claude Larchet (Therapy of Spiritual Illnesses vol.3, p.57-58)
Prayerful Life 