By Grace You Can

I find that some Christians have a good understanding of the extent of our human depravity, but an underdeveloped view of God's vivifying grace. Many seem to believe that because sin continues to cling to and corrupt all our works this side of the resurrection that even as believers we remain fruitless in godliness--incapable of obeying God. But man's total depravity doesn't leave us pessimistic in piety because God's sovereign grace in salvation gives us life, overcomes our weaknesses, and produces a transformed character. By grace we can obey God. I was reading Sibbes today (as we all should), and he said it better than I can.

Beloved, it is part of the new covenant, that whatsoever our duty is, we shall have ability to perform it by the Spirit of Christ; for all the gracious promises of the gospel are not only promises upon condition, and so a covenant, but likewise the covenant of grace is a testament and a will (a will is made without conditions; a covenant with conditions), that as he hath made a covenant what he would have us to do , so his testament is, that we shall have grace to do so; he will put his Spirit into us, and circumcise our hearts, or else, beloved, there would be no more strength of the covenant of grace than there was of that of nature in Adam. Why did Adam fall? He had not the Spirit to uphold him, nor had the promise of it to keep him that he should not fall. Therefore the covenant of works was frustrate. If God should not make good our part as well as his, we should not be saved. Therefore, now in the covenant of grace we may boldly go to God and Christ; and allege unto him, when any duty is pressed upon us, and when we are about to perform any duty, and find want of strength, ‘Lord, thou knowest I have no strength of myself, I am a barren wilderness; but thou hast entered into a covenant of grace with me, which requirest, Lord, in the use of means that thou hast ordained; in attending upon thee, and looking up to thee, I desire that thou wouldst give me strength to submit to thee, to live and die to thee, to direct my course as I should.’ This should be the course of a Christian, and not to set upon things in his own strength; but when duty is discovered, look to the promise of grace and of the Spirit, and put them into suit, and allege them to Christ in the use of sanctified means, as reading, hearing, holy conference, and the like; and he will enable us to do that that is our duty.

Therefore a man may know who is indeed under Christ’s government by this, for he that is actually under Christ’s government and acknowledgeth him to be his Lord, he hath ability to live and die to him in some comfortable measure; to deny himself, to go out of himself, to live and to die to the glory of God. The Spirit of God hath given him this victory and triumph over his own heart.

- Richard Sibbes, Christ's Exaltation Purchased by His Humiliation: The Second Sermon

If you haven't read anything from Sibbes, start with his classic, The Bruised Reed. One of my favorite and most helpful books outside of Scripture. For those who want more, you can pick up his collected works as well.