How powerful is it?
The power of prayer should not be underestimated. James 5:16-18 declares, "…The prayer of a righteous man is powerful and effective. Elijah was a man just like us. He prayed earnestly that it would not rain, and it did not rain on the land for three and a half years. Again he prayed, and the heavens gave rain, and the earth produced its crops." God most definitely listens to prayers, answers prayers, and moves in response to prayers.

Jesus taught, "…I tell you the truth, if you have faith as small as a mustard seed, you can say to this mountain, 'Move from here to there' and it will move. Nothing will be impossible for you" (Matthew 17:20). 2 Corinthians 10:4-5 tells us, "The weapons we fight with are not the weapons of the world. On the contrary, they have divine power to demolish strongholds. We demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ." The Bible urges us, "And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints" (Ephesians 6:18).