From the Anglican Breviary:

OPEN THOU, O LORD, MY MOUTH to bless thy holy name; cleanse also my heart from all vain, evil, and wandering thoughts; enlighten my understanding; enkindle my affections; that I may pray this Office with attention and devotion, and so be meet to be heard in the presence of thy divine Majesty. Through Christ our Lord. Amen.

O LORD, in union with that divine intention wherewith thou thyself on earth didst render thy praises to God, I desire to offer this my prayer unto thee.

From the Philokalia, v. 2:

A BROTHER NAMED JOHN came from the coast to Father Philimon and, clasping his feet, said to him: "What shall I do to be saved? For my intellect vacillates to and fro and strays after all the wrong things."

After a pause, the father replied: "This is one of the outer passions and it stays with you because you still have not acquired a perfect longing for God. The warmth of this longing and of the knowledge of God has not yet come to you." The brother said to him: "What shall I do, father?"

Abba Philimon replied: "Meditate inwardly for a while, deep in your heart; for this can cleanse your intellect of these things." The brother, not understanding what was said, asked the Elder: "What is inward meditation, father?"

The Elder replied: "Keep watch in your heart; and with watchfulness say in your mind with awe and trembling: Lord Jesus Christ, have mercy upon me. For this is the advice which the blessed Diadochos gave to beginners."