Novenas remind us to persevere in prayer. Arranged for nine consecutive days, novenas either pray the same prayer each day or have a different prayer depending on the particular devotion. The first novena of the Church was at Pentecost as Our Lady and the Apostles awaited the coming of the Holy Ghost. Novenas teach us to be patient because God wants us to keep asking for His grace and aid.
Particularly at Pentecost we remember the fruits and gifts of the Holy Ghost, but we should be praying for these every day. A quick list: Gifts ~ wisdom, understanding, knowledge, counsel, fortitude, piety, and fear of the Lord. Fruits ~ charity, joy, peace, patience, long-suffering, goodness, benignity, meekness, fidelity, modesty, contingency, and chastity.
A great saint who truly understood the reality of the presence of the Holy Ghost in our souls when in the state of grace was St. Elizabeth of the Trinity. Her message centered around the divine indwelling. Some great quotes of hers are: "It seems to me that I have found my heaven on earth because my heaven is Thee, my God, and Thou art in my soul. Thou in me and I in Thee, may this be my motto." And again, "What a joyous mystery is Thy presence within me, in that intimate sanctuary of my soul where I can always find Thee, even when I do not feel Thy presence. Of what importance is feeling? Perhaps Thou art all the closer when I feel Thee less." And finally, "May my life be a continual prayer, a long act of love."
There are no words that adequately describe the immense gift of the life of God in the soul. It is a great subject for prayer to dwell on the mystery of God's presence within us. We should make efforts throughout the day and every moment to converse with so great a Guest.