In renouncing our own strength and any thing else which may be regarded as pertaining to ourselves, it is not meant, that we should be inactive and not employ those powers which God has given us; but that in their exercise, we should have no hope, no confidence in them, except so far as they exist in co-operation with an inward divine guidance, and are attended with the divine blessing; in other words, we should have no confidence in them, except so far as the human operation is one with the divine operation.
Or to express the same thing again, in another shape, the great business of the creature is, not to be without action, but to act in concurrence with God, to harmonize with God. This was the prayer of the Savior, “as thou, Father, art in me, and I in thee; that they also may be one in us.” To express the whole as simply and briefly as possible, the sum of religion is unity with God. And this unity, which cannot exist without the concurrence of the creature, is secured by faith. It is not possible for God to be in union with any being, that has not confidence in him. A want of confidence, which is the same thing as a want of faith, is itself disunion.
— edited from The Life of Faith (1852) Part 1, Chapter 7 by Thomas Cogswell Upham. His blog is managed by Craig L Adams and can be found here: http://thomascupham.blogspot.com