One of the first points William Gurnall makes in his Christian in Complete Armor is exactly this - that we must consciously resist our predilection to self-assurance and self-sufficiency, and place all hope for salvation, and all expectation of strength in the Lord's hands.
We cannot worship rightly, resist sin effectively, or do anything that is good apart from the Lord's working in us. There is no hope for any of this apart from His grace active and living in us through the indwelling Holy Spirit and the intercession of the Lord Jesus.
A helpful reminder comes in Gurnall's application section for this doctrine. He writes,
Is the Christian's strength in the Lord, not in himself? Surely then the Christless person must needs be a poor impotent creature, void of all strength and ability of doing anything of itself towards its own salvation. If the ship launched, rigged and with her sails spread cannot stir, till the wind come fair and fill them, much less can the timber that lies in the carpenter's yard hew and frame itself into a ship. If the living tree cannot grow except the root communicate its sap, much less can a dead rotten stake in the hedge, which hath no root, live of its own accord. (p. 23, Christian in Complete Armor, William Gurnall)This drives home the point so clearly. Our life is in HIM. Who derives life and strength? The branch that is drawing life and strength through the sap of the vine. The branch doesn't live by himself... it doesn't do anything apart from that life-giving "spirit". Our self-motivated and self-appointed efforts to do what we think we ought serve to show how poorly we understand this metaphor for Christian life. When we launch out on our own to achieve ends that we have in mind, doing so in our own strength, we pretend in some way as though we are capable apart from Him, even if we confess that doctrine with our lips.
We so desperately want to be in the driver's seat, and to feel capable. The Christian's walk is one of incapability, though, at least as the Bible presents it to us. All we have, all we're able to do, all is the Lord's - our role is one of accepting our own limitations, and receiving His grace, all the while admitting our own state as a humble, unprofitable servant. Nothing more can we be - nothing less should we aim to be - for with our humble acceptance of God's grace and in His strength, we are able to do His work, pleasing and glorifying the Lord of Glory, and building up His Kingdom to His eternal praise. Let it so be, for this is His wonderful and wise decree.