Our prayers are powerful. Look at the power of intercession as seen in Abraham for Lot. Look at the beautiful intercessory prayer Jesus prayed for us in John 17. That is powerful prayer. God said it, that's it.
Prayer is a powerful weapon which can demolish strongholds.
It is to be prayer offered in righteousness, faith, humility, and yet boldly brought before the throne. Through prayer we can change the circumstances which not only surround us, but those for whom we are praying. When we pray as directed, we are to expect the manifestation of the answer as did Paul in Philemon 22. There he told Philemon to prepare a guest room for him that he could come in answer to Philemon's prayers. We are to be prepared for our answers, not surprised.