Summary: Prayer and fasting are useful to enter into a humble, obedient heart condition. But even if a consecrated Christian does have a holy heart condition, that does not mean God will exercise His power to answer that prayer.
Discussion: God uses His loving, just, and wise power according to His will. Consider Jesus, the only begotten Son of God. Jesus, Himself, always obeyed God. Even the words which Jesus spoke were from God. Jesus stated, “…I do nothing of Myself; but as My Father taught Me, I speak these things.” – John 8:28 NKJV Jesus was able to exercise the power of God because He only did the will of God.
We need to study the Bible so that we learn how to pray. It is not acceptable to ask for power, status, wealth, prosperity, health, or to win the lottery. James 4:3 (ESV), “You ask and do not receive, because you ask wrongly, to spend it on your passions.”
For what may we pray?
According to the Lord’s Prayer (Matthew 6:9-14), we may ask for God’s kingdom to come and His will to be done on Earth. Pray for daily bread – but not for lavish feasts. We pray that God will keep us through temptation and deliver us from evil. We are to pray for forgiveness of sins through the blood of Jesus. But Jesus also taught us to ask God to “forgive our sins as we forgive others.” And our whole relationship to God is through Jesus, therefore we pray in the name of Jesus (John 14:13).
Consecrated, spirit-begotten Christians may ask for more of the Holy Spirit (Luke 11:13). They may ask for wisdom (James 1:5). For strength to endure trials (Colossians 1:11). For peace (Romans 14:19). For greater faith and trust (Luke 17:5). For help to develop the fruit of the spirit (Galatians 5:25). For help to witness to others (Romans 10:15).
As you can see, our requests should be about spiritual growth. None of these things are about displays of power, or the promotion of the natural man (Galatians 5:17).
Prayer and fasting are not a formula to prompt God to exercise His power. Obedience results in answered prayer if we pray according to his will.