How did the sorrow of the disciples turn into great joy, directly after the ascension?

According to St. Luke the Evangelist, “He led them out as far as Bethany. And He lifted up His hands and blessed them; Now it came to pass, while He blessed them, He was parted from them, and carried up into heaven; and they worshipped Him and returned to Jerusalem with great joy” (Luke 24:50–52). The cause of this great joy directly after the ascension, is

that the Word of God came down from heaven in the flesh to save humanity and to draw the hearts, minds, and all the energies of His believers towards Him. His ascension to heaven did not take their focus on Him, but rather fixed their eyes towards heaven. Origen says, “If you believe that He sat at the right hand of God in heaven, it would be befitting of you to believe that your place is no longer on the earth, but in heaven.”⁹⁶⁴

St. Athanasius says, “blazing the trial [the Lord] made anew the way up to heaven, saying again, ‘ Lift up your gates, O princes of yours, and be raised up, everlasting gates ’ (Ps. 24:7). For it was not the Word Himself who needed the gates to be opened, since he is the Lord of all, nor was any made thing closed to its Maker; but we were those who needed it, who he himself carried up through His own body. For as He offered [it] to death on behalf of all, so through it he opened up again the way to heaven.”⁹⁶⁵

The monks the Monastery of St. Macarius comment on this, saying, “Here, St. Athanasius is basing his argument on the verse in Hebrews, ‘By a new and living way which He consecrated for us, through the veil, that is His flesh’ (Heb. 10:20). The importance of Christ’s ascension comes from the fact that He was in a human flesh taken from us, and therefore He represented us and whatever He accomplished was for the sake of the entire human race. Since this body belonged to the Word of God, existent in the bosom of the Father, it was His natural right to ascend and to enter into the presence of the Father, becoming the first fruits of humanity and our ambassador before the Father.”⁹⁶⁶