Do I sustain myself for salvation? Or Does God sustain me?

Is my salvation dependent on me? Or does God sustain my salvation? Is God the one who has saved me from wrath? Is God the good shepherd who guards his sheep? Do the sheep guard themselves from thieves and carnivores?

The Apostle John records Jesus as saying "My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father's hand. I and the Father are one.” (Read John 10 in its entirety)

Paul, the master theologian, wrote in his letter to the Romans: For those whom he foreknew he also predestined to be conformed to the image of his Son, in order that he might be the firstborn among many brothers. And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified. 

What then shall we say to these things? If God is for us, who can be against us? He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things? Who shall bring any charge against God's elect? It is God who justifies. Who is to condemn? Christ Jesus is the one who died—more than that, who was raised—who is at the right hand of God, who indeed is interceding for us. Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or danger, or sword? As it is written,

“For your sake we are being killed all the day long;
    we are regarded as sheep to be slaughtered.”

No, in all these things we are more than conquerors through him who loved us. For I am sure that neither death nor life, nor angels nor rulers, nor things present nor things to come, nor powers, nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord.

The Apostle Peter wrote in his letter to the Christians in Asia Minor: Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead, to an inheritance that is imperishable, undefiled, and unfading, kept in heaven for you, who by God's power are being guarded through faith for a salvation ready to be revealed in the last time.

These are but a few verses from the Bible that speak of God guarding the Christian's salvation. From what I understand salvation is completed for the Christian. If this is correct the Christian can find rest in this knowledge. He should let it seep into his heart. She should be thankful. If the Christian is clothed in the righteousness of Christ and that is what God sees when he looks at the Christian then I would assume a habit of gratefulness for God's gift would be built in the Christian. I wouldn't think a life of moral carelessness would be adopted by the Christian if this knowledge has seeped into her soul.

What can we gather from this data? That God loves his children warts and all (to borrow a phrase from Sproul); that God guards his children's salvation and his children can rest in this knowledge knowing they will get their inheritance promised to them by their God.