10 Finally, be strong in the Lord and in the strength of his might. 11 Put on the whole armour of God, that you may be able to stand against the schemes of the devil.12 For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. 13 Therefore take up the whole armour of God, that you may be able to withstand in the evil day, and having done all, to stand firm. 14 Stand therefore, having fastened on the belt of truth, and having put on the breastplate of righteousness, 15 and, as shoes for your feet, having put on the readiness given by the gospel of peace. 16 In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one;17 and take the helmet of salvation, and the sword of the Spirit, which is the word of God, 18 praying at all times in the Spirit, with all prayer and supplication. To that end, keep alert with all perseverance, making supplication for all the saints."
Ephesians 6:10-18
For one thing, the whole area of 'wrong thinking' has an element of the evil one's influence in it - one has only to mention words like 'heresy' or 'brain-washing' to realise the extent to which the enemy of souls is so often at work in modern life. The New Testament concept of 'seducing spirits' (1 Timothy 4:1) is to be taken in all seriousness! For another thing, however, and in a much more mundane sense, it is so easy for believers to be nudged unwittingly into attitudes of introspection and self-preoccupation that become highly detrimental to true spiritual health - my spiritual state, my spiritual progress, my spiritual battles, my spiritual hunger and longings - attitudes which prompt the question, Do we ever escape from ourselves? In such a mind-set we surely need the wind of God to blow through us, bringing much-needed fresh air to remove the spiritual cobwebs from our thinking. In contrast to this we may well think of the Apostle John's attitude and experience on the Isle of Patmos (Revelation 1:5). How easily he could have become preoccupied with his trying circumstances, but instead his mind was lifted up heavenwards in the glorious doxology, 'Unto Him that loved us, and washed us from our sins in His own blood, and hath made us kings and priests unto God and His Father; to Him be glory and dominion forever and ever. Amen'. It is all a question of allowing our minds and thoughts to be captured and mastered by something bigger and greater than ourselves. To spend time day by day thinking of what we are in Christ and what God has made us in Him, to think of our high calling and destiny as sons and daughters of God, to think of the greatness of His redeeming love - it is not possible but that this should have an unmistakeable effect on our whole way of life.
The eternal glories gleam afar
To nerve my faint endeavour
This is the use, and the point, of wearing the helmet of salvation!