Imagine what the eleven Apostles felt. They saw His death (well, only John was at the crucifixion), utter sadness and dispair. Then His Resurrection, utter joy only to have Him ascend upon clouds and disappear, sadness again. The time between that and the arrival of the Holy Spirit must have been, I can’t imagine, what could they do but pray in that upper room with His Mother, Mary. Our Eastern Catholic calendar still shows one more week of the Ressurection season, though after Ascension the curtain separating the altar is closed, it had been opened wide since Ressurection Day (Easter-Pascha). It was sad to see that.