He spoke a parable unto them… that men ought always to pray, and not to faint (Luke 18:1).
No temptation in the life of intercession is more common than this of failure to persevere. We begin to pray for a certain thing; we put up our petitions for a day, a week, a month; and then, receiving as yet no definite answer, straightway we faint, and cease altogether from prayer concerning it.
This is a deadly fault. It is simply the snare of many beginnings with no completions. It is ruinous in all spheres of life. The man who forms the habit of beginning without finishing has simply formed the habit of failure. The man who begins to pray about a thing and does not pray it through to a successful issue of answer has formed the same habit in prayer. To faint is to fail; then defeat begets disheartenment, and unfaith in the reality of prayer, which is fatal to all success.
But someone says, "How long shall we pray? Do we not come to a place where we may cease from our petitions and rest the matter in God's hands?" There is but one answer. Pray until the thing you pray for has actually been granted, or until you have the assurance in your heart that it will be. Only at one of these two places dare we stay our importunity, for prayer is not only a calling upon God, but also a conflict with Satan. And inasmuch as God is using our intercession as a mighty factor of victory in that conflict, He alone, and not we, must decide when we dare cease from our petitioning. So we dare not stay our prayer until the answer itself has come, or until we receive the assurance that it will come.
In the first case we stop because we see. In the other, we stop because we believe, and the faith of our heart is just as sure as the sight of our eyes; for it is faith from, yes, the faith of God, within us.
More and more, as we live the prayer life, shall we come to experience and recognize this God-given assurance, and know when to rest quietly in it, or when to continue our petitioning until we receive it.
--The Practice of Prayer
Tarry at the promise till God meets you there. He always returns by way of His promises.