When the Spirit of God comes down to man and overshadows him with the fullness of His inspiration, then the human soul overflows with unspeakable joy, for the Spirit of God fills with joy whatever He touches.
This is that joy of which the Lord speaks in His Gospel: A woman when she is in travail has sorrow, because her hour is come; but when she is delivered of the child, she remembers no more the anguish, for joy that a man is born into the world.
In the world you will be sorrowful; but when I see you again, your heart shall rejoice, and your joy no one will take from you (Jn. 16:21-22).
Yet however comforting may be this joy which you now feel in your heart, it is nothing in comparison with that of which the Lord Himself by the mouth of His Apostle said that that joy eye has not seen, nor ear heard, nor has it entered into the heart of man what God has prepared for them that love Him (I Cor. 2:9).
Foretastes of that joy are given to us now, and if they fill our souls with such sweetness, well-being and happiness, what shall we say of that joy which has been prepared in heaven for those who weep here on earth? And you, my son, have wept enough in your life on earth; yet see with what joy the Lord consoles you even in this life!
Now it is up to us, my son, to add labours to labours in order to go from strength to strength (Ps. 83:7), and to come to the measure of the stature of the fullness of Christ (Eph. 4:13), so that the words of the Lord may be fulfilled in us:
But they that wait upon the Lord shall renew their strength; they shall grow wings like eagles; and they shall run and not be weary (Is. 40:31); they will go from strength to strength, and the God of gods will appear to them in the Sion (Ps. 83:8) of realization and heavenly visions.
Only then will our present joy (which now visits us little and briefly) appear in all its fullness, and no one will take it from us, for we shall be filled to overflowing with inexplicable heavenly delights.
Seraphim of Sarov (Orthodox Church; 1759-1833): On the Acquisition of the Holy Spirit.