The enemy of our salvation especially strives to draw our heart and mind away from God when we are about to serve Him, and endeavours to adulterously attach our heart to something irrelevant. Be always, every moment, with God, especially when you pray to Him. If you are inconstant, you will fall away from life, and will cast yourself into sorrow and straitness.
When you are praying alone, and your spirit is dejected, and you are wearied and oppressed by your loneliness, remember then, as always, that God the Trinity looks upon you with eyes brighter than the sun; also all the angels, your own Guardian Angel, and all the Saints of God. Truly they do; for they are all one in God, and where God is, there are they also. Where the sun is, thither also are directed all its rays. Try to understand what this means.
Until we have acquired true prayer, we are like those who introduce children to walking. Make the effort to raise up, or rather, to enclose your mind within the words of your prayer; and if, like a child, it gets tired and falters, raise it up again. The mind, after all, is naturally unstable, but the God Who can do everything can also give it firm endurance. Persevere in this, therefore, and do not grow weary...
Tedium is the granddaughter of despondency, and the daughter of slothfulness. In order to drive it away, labor at your work, and do not be slothful in prayer. The tedium will pass, and zeal will come. And if to this you add patience and humility, then you will be rid of all misfortunes and evils.
Prayer is a branch (of a tree) of meekness, and freedom from anger. Prayer is an expression of joy and thankfulness. Prayer is a remedy against sorrow and depression.
A great effort and much toil are needed in prayer before we can reach a state in which our mind is no longer troubled, and so attain the inward heaven of the heart where Christ dwells. As St. Paul says, 'Do you not realize that Christ dwells within you, unless you are worthless?' (cf. 2 Cor. 13:5).
Ask the angels and the saints to intercede for you, just as you'd ask people who are alive. Stand face to face with them, in the belief that they are also standing face to face with you.
Do not pray that things may be according to your desires, for they are not always in keeping with the will of God. Better pray as you were taught, saying: ‘Thy will be done’ on me (Matt. vi 10). And ask thus about all things, for He always desires what is good and profitable for your soul, whereas you do not always seek it.
The one who prays ought never to halt his movement of sublime ascent toward God. For just as we should understand the ascent 'from strength to strength' as the progress in the practice of the virtues, 'from glory to glory' (2 Cor. 3:18) as the advance in the spiritual knowledge of contemplation, and the transfer from the letter of sacred writing to its spirit, so in the same way the one who is settled in the place of prayer should lift his mind from human matters and the attention of the soul to more divine realities.