Finally, my brethren, be strong in the Lord, and in the power of his might. Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand. Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness; And your feet shod with the preparation of the gospel of peace; Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked. And take the helmet of salvation, and the sword of the Spirit, which is the word of God: Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints;
Ephesians 6:10, 13-18
God demands that we be strong, but the strength does not originate from us but from the Lord. He wants us to firmly lay hold on his mighty power with which he rose our Lord Jesus Christ from the dead. All the armour of God we are commanded to put on to be able to withstand against all the onslaughts of the devil is meant to equip us to engage in prayer warfare effectively. The real war is fought and won in prayers. Note it is through prayers that we truly access his mighty power.