Pray constantly! (1 Thessalonians 5:17). M'Cheyne talks about prayer:
“Your prayers are not lost” by Robert Murray M’Cheyne:
“God’s children, should pray. You should cry day and night unto God. God hears every one of your cries, in the busy hour of the daytime, and in the lonely watches of the night. He treasures them up from day-to-day; soon the full answer will come down: ‘He will answer speedily.’
Christ never loses one believing prayer. The prayers of every believer, from Abel to the present day, He heaps upon the altar, from which they are continually ascending before His Father and our Father; and when the altar can hold no more, the full, the eternal answer will come down.
Do not be discouraged, dearly beloved, because God bears long with you—because He does not seem to answer your prayers. Your prayers are not lost. When the merchant sends his ships to distant shores, he does not expect them to come back richly laden in a single day: he has long patience.
‘It is good that a man should both hope and quietly wait for the salvation of the Lord.’ Perhaps your prayers will come back, like the ships of the merchant, all the more heavily laden with blessings, because of the delay.”
–Robert Murray M’Cheyne, “Fourth Pastoral Letter: Edinburgh, February 20, 1839″ in Robert Murray M’Cheyne and Andrew A. Bonar, Memoir and Remains of the Rev. Robert Murray McCheyne (Edinburgh; London: Oliphant Anderson & Ferrier, 1894), 193-194.