Do I know exactly what God desires in every specific detail of this life, or even of this day? I do not, but when I pray I do not pray alone. The Holy Spirit – who DOES know exactly what God desires – prays with me, prays for me, and intercedes for me: He fills in the gap between my limited life/understanding and the omniscience of our all-loving Father.
He does the same for you, as well. That’s why all things work together for good!
Romans 8:26-28 (NKJV)
26 Likewise the Spirit also helps in our weaknesses. For we do not know what we should pray for as we ought, but the Spirit Himself makes intercession for us with groanings which cannot be uttered. 27 Now He who searches the hearts knows what the mind of the Spirit is, because He makes intercession for the saints according to the will of God. 28 And we know that all things work together for good to those who love God, to those who are the called according to His purpose.