Saint Augustine explains that by persevering in prayer, we expand our capacity to receive the gift that God is already preparing to give us.
In Luke 11:9, Our Lord teaches His disciples to persevere in prayer, telling them, "[E]very one that asks, receives; and he that seeks, finds; and to him that knocks, it shall be opened." In Matthew 6:8, however, Our Lord reveals that God already knows our needs beforehand: "[Y]our Father knows what is needful for you, before you ask him."
So the question arose in the early Church of what's accomplished by asking God for something when He already knows what we need. Saint Augustine, Father and Doctor of the Church, answers that question as early as the fourth century.
God is already mindful of what we really need, says the saint, and is preparing to give us that exact gift while we're still persevering in prayer. God must wait until we're prepared to receive the gift by the ongoing process of asking for it.
In a fourth-century letter to Proba, a devout Catholic widow, St. Augustine wrote:
God ... wants us rather to exercise our desire through our prayers, so that we may be able to receive what He is preparing to give us. His gift is very great indeed, but our capacity is too small and limited to receive it. ... The deeper our faith, the stronger our hope, the greater our desire, the larger will be our capacity to receive that gift, which is very great indeed.
Watch the panel discuss the need for spiritual perseverance in The Download—Never Stop Praying.