I found this exquisite little prayer in a book called the Raccolta from 1866. Raccolta, which means “collection” in Italian, is a book of prayers sanctioned by the Catholic Church back in 1807. Abbreviated from “Collection of Prayers and good works for which the Supreme Pontiffs have granted Holy indulgences.” 

I would like to thank the team at the Liturgia Latina Project for providing the full translation. http://www.liturgialatina.org/

Holy Spirit, sweet Guest of my soul, abide in me and grant that I may ever abide in Thee.

O Holy Spirit, Spirit of truth, come into our hearts; shed the brightness of Thy light upon the nations, that they may please Thee in unity of faith

Amen.