To will one thing

The following is the introductory prayer to Soren Kierkegaard's book, Purity of Heart. It pretty much says it.

"Father in Heaven! What is a man without Thee! What is all that he knows, vast accumulation though it be, but a chipped fragment if he does not know Thee! What is all his striving, could it even encompass a world, but a half-finished work if he does not know Thee: Thee the One, who art one thing and who art all! So may Thou give to the intellect, wisdom to comprehend that one thing; to the heart, sincerity to receive this understanding; to the will, purity that wills only one thing. In prosperity may Thou grant perseverance to will one thing; amid distractions, collectedness to will one thing; in suffering, patience to will one thing. Oh, Thou that giveth both the beginning and the completion, may Thou early, at the dawn of day, give to the young man the resolution to will one thing. As the day wanes, may Thou give to the old man a renewed remembrance of his first resolution, that the first may be like the last, the last like the first, in possession of a life that has willed only one thing.

"Alas, but this has indeed not come to pass. Something has come in between. The separation of sin lies in between. Each day, and day after day something is being placed in between: delay, blockage, interruption, delusion, corruption. So in this time of repentance may Thou give the courage once again to will one thing. True, it is an interruption of our ordinary tasks; we do lay down our work as though it were a day of rest, when the penitent (and it is only in a time of repentance that the heavy-laden worker may be quiet in the confession of sin) is alone before Thee in self-accusation. This is indeed an interruption. But it is an interruption that searches back into its very beginnings that it might bind up anew that which sin has separated, that in its grief it might atone for lost time, that in its anxiety it might bring to completion that which lies before it. Oh, Thou that gives both the beginning and the completion, give Thou victory in the day of need so that what neither a man's burning wish nor his determined resolution may attain to, may be granted unto him in the sorrowing of repentance: to will only one thing."

Soren Kierkegaard (1846)

Things needed for spiritual growth

Many are the things of which the believer has need in order to attain knowledge of God and virtue: deliverance from passions, patient acceptance of trials, the inner principles of virtues, the practice of methods of spiritual warfare, the uprooting of the soul's predilection for the flesh, the breaking of the senses' attachment to sensible objects, the utter withdrawal of the intellect from all created things; and, in short, there are countless other things which help us to reject sin and ignorance and to attain knowledge and virtue. It was surely because of this that the Lord said, "Whatever you ask for in prayer, believing, you will receive" (Matthew 21:22), stating simply that the devout must seek and ask with understanding and faith for all those things, and for those alone, which lead to virtue and knowledge of God. For all these things are profitable, and unquestionably the Lord gives them to those who ask.

--Maximos the Confessor (580-662)