J.C. Ryle on the parable of the Widow and the Judge (Luke 18:1-8):
“Do we ever feel a secret inclination to hurry our prayers, or shorten our prayers, or become careless about our prayers, or omit our prayers altogether? Let us be sure, when we do, that it is a direct temptation from the devil. He is trying to sap and undermine the very citadel of our souls, and to cast us down to hell. Let us resist the temptation, and cast it behind our backs. Let us resolve to pray on steadily, patiently, perseveringly, and let us never doubt that it does us good. However long the answer may be in coming, still let us pray on. Whatever sacrifice and self-denial it may cost us, still let us pray on, ‘pray always,’ – ‘pray without ceasing,’ – and ‘continue in prayer.” Let us arm our minds with this parable, and while we live, whatever we make time for, let us make time for prayer.”
-J.C. Ryle, Expository Thoughts On the Gospels, Volume 2. (Grand Rapids, MI: Baker, 2007), 253-254.