The manifestation of God's power is not available at our discretion or timing. It takes a release of faith from God upon us, as willing vessels waiting on the Father, to do all that He tells us. His promises are ours but the timing and dispensation are His. We see Christians claiming His promises and power all the time, and we very often witness their disappointment and confusion when the situation fails to change. Many have fallen away because of this kind of faith. True faith that acts on Gods behalf comes from Him. Yet you will hear others contend that it was due to a lack of our own faith that failed to bring the power. God's word teaches us that even when we're faithless He is faithful.
Gods promises are intended to give us faith, hope, and love- the result of an intimate relationship with Him. When God's Word is commanded without this intimacy, or direction from the Holy Spirit, the claimants are exercising a faith of their own and are not genuinely compassionate for their hearers. They are only interested in control and being perceived by others as someone very spiritual. Listeners may be impressed or influenced, but if they become a part of that sheepfold, they will subject themselves to a false shepherd, both pursuing only of the power and gifts of God, but not God Himself. Should you think these shepherds and sheep are still okay in the sight of God, listen carefully to what Jesus says about them. "Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness." (Matthew 7:21-23) It's interesting that He calls them 'workers of lawlessness', but it makes sense in light of Matthew 22:37-40: "You shall love the Lord your God with all your heart and with all your soul and with all your mind. This is the great and first commandment. And a second is like it: You shall love your neighbor as yourself. On these two commandments depend all the Law and the Prophets." Without God's life, one can not know love.
The purpose of God's promises is intended for us to trust Him regardless of any outcome, living by the faith He has given us. If we were to have the authority of God's word at our discretion, where then would His sovereign power and glory be? It would belong to us, needing nothing more from Him. Our hope should rest on His word which states that what is impossible for man is possible for God, not something we can pocket and pull out at our own discretion. We must become empty and available for God to work through us according to His will. The true working out of God's promises in our lives happens when we have died to ourselves and no longer live, but it is Christ who lives in us.
"Let each of you look not only to his own interests, but also to the interests of others. Have this mind among yourselves, which is yours in Christ Jesus,who, though he was in the form of God, did not count equality with God a thing to be grasped, but made himself nothing, taking the form of a servant, being born in the likeness of men." (Philippians 2:4-7)