John Chrysostom — as excerpted in the Catena Aurea on John 16:16-22

“(Hom. lxxix) Our Lord after having relieved the spirits of the disciples by the promise of the Holy Spirit, again depresses them: A little while, and ye shall not see Me. He does this to accustom them to the mention of His departure, in order that they may bear it well, when it does come. For nothing so quiets the troubled mind, as the continued recurrence to the subject of its grief.”