The Ascension plants Man in the heart of Heaven. That's why the Glorious Mystery of the Ascension is traditionally associated with prayer for the virtue of Hope. Hope is oriented, not so much toward the future, as toward the fact that the same God we have known and know now is not going to abandon us. Temporally speaking, we have no hope. The future is ultimately that time when we and everybody we know will be dead. But eternally speaking, we have great hope. For we shall be with Christ in eternity.
This curious mixture of temporal loss and eternal hope is reflected in the curious fact that Jesus' promise not to abandon us comes at the moment when Jesus leaves us.
You shall receive power when the Holy Spirit has come upon you; and you shall be my witnesses in Jerusalem and in all Judea and Samaria and to the end of the earth." And when he had said this, as they were looking on, he was lifted up, and a cloud took him out of their sight (Acts 1:8-9).
But then, as Luke makes clear, Jesus is not really leaving. For the Gospel Luke has just written only tells us of what Jesus "began" to do and teach. His entire earthly ministry is only the spark. The Church, filled with His Spirit, is the Fire and he is now to continue his work in a way more intimate with us than it was during his earthly ministry. He is with us always, but he is also "seated at the right hand of the Father" in Heaven. And where our Great Pioneer has already gone, we will one day go as well. That's why he himself said, "But now I am going to him who sent me; yet none of you asks me, 'Where are you going?' But because I have said these things to you, sorrow has filled your hearts. Nevertheless I tell you the truth: it is to your advantage that I go away, for if I do not go away, the Counselor will not come to you; but if I go, I will send him to you" (John 16:5-7).