"As a Christian soldier you must always stand in a defensive posture with your armor on, ready to defend the treasure God has given you to keep.
"And take the helmet of salvation" Ephesians 6:17. These words of Scripture present us with another piece in the Christian's armor-- the helmet of salvation to cover his head in the day of battle. This helmet, together with most of the other pieces of armor, are defensive arms, to protect the Christian from sin but not to keep him from suffering.
Only one piece in the whole armor is for offense-- the sword. Scripture hints that the Christian's war lies chiefly on the defense and therefore requires defensive arms to fight it. God has deposited a rich treasure of grace in every saint's heart, which the devil spitefully tries to rob the Christian of by waging a bloody war against him. And so the believer overcomes his enemy when he himself is not overcome. He wins the day when he does not lose his grace, his work being to keep what is his rather than to get what is the enemy's. Because the saint's war lies chiefly on the defense, we must instruct the Christian how to manage combat with both Satan and his weapons of war.
As a Christian soldier you must always stand in a defensive posture with your armor on, ready to defend the treasure God has given you to keep, and to repel Satan's assaults. But do not step outside the line of your calling which God has drawn about you. Let Satan be the assailant and come if he will to tempt you; but do not go out and tempt him to do it.
Even when the devil's instruments of war reproach the Christian, the Gospel does not allow him to use the devil's weapons to return them stroke for stroke. "Be pitiful, be courteous: not rendering evil for evil, or railing for railing: but contrariwise blessing" 1 Peter 3:8-9. You have a girdle and breastplate to defend you from their bullets-- the comfort of your own sincerity and holy walk. With these you can repel the sordid arsenal thrown at you-- but there is no weapon for self-revenge.”
Quoted material from, ”The Christian in Complete Armour Daily Readings in Spiritual Warfare” by Gurnall and James S Bell. http://www.moodypublishers.com/pub_productDetail.aspx?id=41823&pid=53617