Joel Beeke was a participant at the most recent Desiring God Conference for Pastors and is the author of many books, a couple of which I picked up this week. In Living by God’s Promises, Beeke and LaBelle offer this nugget of assurance about prayer:
The promises of God are the rule of prayer. Just as we hope for and believe what God has promised, so we must pray for what God has promised. David makes this evident in 2 Samuel 7:27, when he prays, “For thou, O LORD of hosts, God of Israel, hast revealed to thy servant, saying, I will build thee an house: therefore hath thy servant found in his heart to pray this prayer unto thee” (cf. Luke 1:38). Having the promise of God in hand not only emboldened David’s hope and strengthened his faith, but it also fed and informed his prayer. Truly, we do not have a prayer without the promises of God (emphasis mine).
Beeke and LaBelle, pp. 2-3.