The following is taken from Dom Scupoli's The Spiritual Combat.
Prayer is the channel of all Divine grace; by it God is compelled, as it were, to grant us the strength of Heaven, and destroy by our weak hands the fiercest of our foes. But in order to receive full benefit from our prayer, the following method should be observed:
1. We must desire sincerely to serve God with ardent fervor in the manner most agreeable to Him; and this desire will be enkindled within our breasts if we consider three things attentively. The first is that Almighty God deserves our homage and service by reason of the excellence of His sovereign being, His goodness, beauty, wisdom, power, and His ineffable, infinite perfection. The second is that God in Heaven became man on earth to consecrate a life of thirty-three years to the cause of our salvation. He condescended to dress our wounds with His own hands, and heal them, not with oil and wine, but with His own precious blood and immaculate body, torn and disfigured by cruel whips, thorns, and nails. The third point is our realization of the obligation to observe His law, and discharge every duty, since this is the only way we can expect to triumph over the devil, to become masters of ourselves, and children of God.
2. We must have a vibrant, living faith and a firm confidence that God will not refuse the assistance necessary to serve Him faithfully and work out our salvation. A soul rekindled with this holy confidence is like a sacred vessel, into which Divine Mercy pours the treasures of His grace; and the larger the vessel, the greater the abundance of Heavenly blessings it receives through prayer. For how can God, Whose power is limitless, and Whose goodness is alien to all deception, ever refuse His gifts to those whose petitions He has encouraged, and whose perseverance and faith He has promised to reward with the blessings of the Holy Spirit?
3. But our motive for prayer must be the will of God rather than the will of self. We must apply ourselves to this divinely appointed duty because He has commanded it, and we must wish no more than that which is in utter conformity to God's plan. Thus, our intention will not be to make the Divine will subservient to our own, but rather, to transform the human will so that it is in complete harmony with the Divine. The reason for this humble accedence to the Divine will is the perversity of our own, tainted as it is with a blind self-love. Guided by ourselves alone, we would err and stumble, but the will of God, essentially just and holy, cannot be mistaken. Thus the will of God should be the will of men, since not to follow the former is to go astray. Let us, then, be most solicitous that all our petitions be agreeable to God, and if doubts arise concerning the concurrence of the human with the Divine, let a humble submission to Divine Providence accompany our requests. If, however, the things we ask are, by their very nature, pleasing to Him, such as grace, virtue, etc., then let us beg them with a view to pleasing and serving His Divine Majesty, rather than for any other consideration, however creditable.
4. If we wish our prayers to be efficacious, our actions must suit the petitions, and we must exert much energy in making ourselves worthy of the favors we ask. For prayer and interior mortification are inseparable, and he that seeks a particular virtue, without making a serious effort to practice it, only tempts God.
5. Before we ask anything of God, we ought to thank Him most humbly for the innumerable benefits He has graciously bestowed upon us. Let us say to Him: "O Lord, Who after creating me, didst mercifully pay the price of my redemption, delivering me from the fury of myriad enemies, come now to my assistance; and forgetting my past ingratitude, bestow upon me this favor I now ask."
If, however, at the very time we seek to attain a particular virtue, we find ourselves tempted to the contrary vice, let us thank God for granting us the opportunity of practicing the virtue in question, and look upon the occasion as a favor.
6. As the entire force and efficacy of prayer is attributed solely to the goodness of God, at the conclusion of our petitions we should constantly remember the merits of our Savior's life and passion, and His promise to graciously hear our requests, with one or the other of these sentences:
a) "I beseech Thee, O Lord, through Thy infinite mercy, to grant my petition."
b) "Through the merits of Thy Son, bestow this favor on me."
c) "Be mindful, O God, of Thy promises, and hear my prayers."
Again, we may have recourse to the intercession of the blessed Mother and the other Saints; for they prevail much with God, Who is pleased to honor them, in proportion to the honor they accorded Him on earth.
7. We must persist in prayer, since God certainly cannot overlook our humble perseverance. For if the pleadings of the widow in the Gospel prevailed with the wicked judge, how can our pleadings be ignored by God, Who is infinitely good? Thus, although our favors may not be immediately granted, and may even appear to be ignored by God, we must not lose our confidence in His infinite goodness, nor desist from prayer. For God possesses both immense power and will to grant us those things conducive to our ultimate welfare. Therefore, if we are not wanting in ourselves, we shall inevitably obtain what we ask for, something better, or perhaps both. As for the rest, the more we churlishly think ourselves slighted by God, the more we should hold ourselves in contempt. But in considering our misery, we should contemplate the Divine mercy, and far from lessening our confidence in Him, we must increase it; for the steadier we remain in situations attended by fear and diffidence, the greater will be our merit.
Finally, let us never cease to thank God, blessing equally His wisdom, His goodness, His charity, whether He grants or refuses our petition. Whatever happens, let us be undisturbed, con- tented and resigned to divine Providence in all things.