Paul says it twice: “Put on the full armor of God.” Why? “So that you can take your stand against the devil’s schemes” and “so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand.”
Paul then speaks of “our struggle.” (Ephesians 6:12)
Obviously, we do have a struggle after our salvation. And what is this struggle? We struggle to stand our ground. In taking a stand, we wrestle “against the powers of this dark world.” We also struggle “against the spiritual forces of evil in the heavenly realms.” We struggle here on earth; we struggle “in the heavenly realms” which is not to say we struggle in heaven itself. Rather, some of our struggles are physical; others are spiritual.
To withstand and even “extinguish all the flaming arrows of the evil one,” (Ephesians 6:16) we need truth, righteousness, readiness in the gospel of peace, faith, our salvation, and God the Holy “Spirit, which is the Word of God.” (Ephesians 6:17) We need to “be alert” and “keep on praying for all the saints.” (Ephesians 6:18)
Paul calls on us to “be strong in the Lord and in His mighty power.” (Ephesians 6:10)