The following is taken from The Valley of Vision: A Collection Of Puritan Prayers And Devotions. It provides a wonderful collection of devotional thoughts on abiding in Christ that we might carry out fruitful life in the battle.
O Lord, I bless you that the issue of the battle between yourself and Satan has never been uncertain, and will end in victory.
Calvary broke the dragon’s head, and I contend with a vanquished foe, who with all his subtlety and strength has already been overcome.
When I feel the serpent at my heel may I remember him whose heel was bruised, but who, when bruised, broke the devil's head.
My soul with inward joy extols the mighty conqueror.
Heal me of any wounds received in the great conflict; if I have gathered defilement, if my faith has suffered damage, if my hope is less than bright, if my love is not fervent, if some creature-comfort occupies my heart, if my soul sinks under pressure of the fight.
O you whose every promise is medication, every touch life, draw near to your weary warrior, refresh me, that I may rise again to wage the strife, and never tire until my enemy is trodden down.
Give me such fellowship with you that I may defy Satan, unbelief, the flesh, the world, with delight that comes not from a creature, and which a creature cannot mar.
Give me a drink of the eternal fountain that lies in your immutable, everlasting love and decree.
Then shall my hand never weaken, my feet never stumble, my sword never rest, my shield never rust, my helmet never shatter, my breastplate never fall, as my strength rests in the power of your might.