Ephesians 6:11 “Put on the whole armour of God, that ye may be able to stand against the wiles of the devil.”
Being fully outfitted with the armor of God was so important to Paul as he was writing that he went on to give virtually the same command in verse 13, “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.”
A soldier who he not fully equipped for the fight doesn’t stand much of a chance. When a soldier has all his necessary equipment but neglects to use it, he or she is begging for trouble. The same goes for a soldier who will take the equipment and not train how to properly use it. He is leaving himself vulnerable to attack. 1 Kings 22 tells us about king Ahab doing this. Ahab wasn’t used to wearing armor, he wore his kingly robes, so when he went out to battle his armor wasn’t properly secured on him. An archer decided to do some moving target practice and hit Ahab between the joints or seems of his armor, mortally wounding him.
When we as Christians neglect our armor in some way we are leaving ourselves exposed. I can walk around with a sword as big as Conan’s and wield it with the best of them but if I lack any of the other parts of the armor the enemy will find those weaknesses. The sword by itself is powerful but God didn’t give us just the sword. It all goes together and must be used in unison.
Also we must know how to use the different pieces. For example (please forgive me for such a crude example but it really fits the bill) how many times has an award show been aired and one of the women has a wardrobe malfunction? Suddenly she is partially exposed for all to see what God meant for only her husband to look at. It happened because although the dress was tailored for her she had never worn it before and thus didn’t know how to wear it to prevent such an outburst (of course that it was so daring to begin with doesn’t help). My point is we must stay in the word of God every day, pray every day about everything, be in church when the doors are open, and forsake our natural desire for sin. By doing this we are training with our armor on, I know we will not be sinless but proper usage will make us sin less. So yes we need the whole armor all the time.