If you were going into battle and your life depended upon the outcome, would you go dressed in your undies? I don’t think so. Yet, people run around in their spiritual drawers all the time, or even in their birthday suits.
Armor might seem cumbersome if it wasn’t made to fit the wearer in a precise manner. One might be tempted to leave off the helmet, but that would leave the head vulnerable. Forget your breastplate and your heart and lungs are open for mortal wounds. Each piece is important and protects a different part of the person. When we put on the whole armor of God, we are covered, protected, and ready for battle in a covering precisely made to fit each of us.
10 Finally, my brethren, be strong in the Lord and in the power of His might. 11 Put on the whole armor of God, that you may be able to stand against the wiles of the devil. 12 For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age,[a] against spiritual hosts of wickedness in the heavenly places. 13 Therefore take up the whole armor of God, that you may be able to withstand in the evil day, and having done all, to stand.
14 Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness, 15 and having shod your feet with the preparation of the gospel of peace; 16 above all, taking the shield of faith with which you will be able to quench all the fiery darts of the wicked one. 17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God; 18 praying always with all prayer and supplication in the Spirit, being watchful to this end with all perseverance and supplication for all the saints— 19 and for me, that utterance may be given to me, that I may open my mouth boldly to make known the mystery of the gospel, 20 for which I am an ambassador in chains; that in it I may speak boldly, as I ought to speak.”
If we intend to survive the battle, we need to use all of our defenses and put on our whole armor.