In the Orthodox Church it is customary to begin all private prayers as well as church services by first addressing the Holy Spirit in a special prayer and asking Him to renew His grace within us. This prayer, which starts with the words "O Heavenly King," is remarkable in that it consists of the words said by our Lord Jesus Christ and it guides a Christian toward what is important to ask from God.
O Heavenly King, Comforter, Spirit of Truth, Who art everywhere and fillest all things, Treasury of Blessings and Giver of Life, come and abide in us, and cleanse us from every impurity, and save our souls, O Good One.
Here we address the Holy Spirit as "Heavenly King" because He is the third Person of the Holy Trinity, equal to the Father and His Son. He is called the Comforter because He consoles the believers and gives them joy in time of grief. He is called the Spirit of Truth as He reveals to the faithful the realities of spiritual life and helps them to love the truth. He is omnipresent because the divine nature has no bounds or obstacles. He is called the treasury of blessings and the giver of Life as He is the ultimate source of everything that is of value. He gave life to all of nature and, in particular, higher spiritual life to human beings and angels.
Addressing the Holy Spirit in this way, we ask Him, the Almighty, to cleanse us from every passion which originates within us or attaches to us in dealing with sinful people. We ask Him to stay within us and guide us to eternal salvation. When praying to the Holy Spirit and asking for different spiritual gifts, one should preserve a humble attitude and recognize his unworthiness because "God opposes the proud but gives grace to the humble."