…men ought always to pray, and not to faint… – Luke 18:1

“Long as they live should Christians pray,
For only while they pray they live.”

When they are under the wings of the cherubim crying unto God at His mercy seat then are they in the secret place of the tabernacle of the Most High, and then shall they abide under the shadow of the Almighty.

We ought to be constant in prayer because such remarkable gifts are vouchsafed to importunity. God often gives liberally to prayer when it speaks but once, but frequent pleading begets abundant answering. That is the most soul-enriching prayer which is long in winning its way with God. When prayers like great ships have been long on the voyage you may hope that they have gone far and have gathered rich cargoes and will come home freighted with all the goodlier merchandise. If you can but quietly hope, and patiently wait, all will be well. The very choicest blessings of heaven are reserved for the Elijahs who can say, “Go again seven times,” for the men who come again and again and again and never faint. Wait then upon the Lord with holy importunity of prayer, and your reward shall more than repay you. It is good for us to be compelled to pray like this; it brings us up from spiritual childhood to perfect manhood. Therefore be ye constant in prayer, and gather strength for importunate pleadings. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1480.cfm