What reason have you that you would think that you can suddenly change the inclination of your heart and actions, and become a new man? The odds are surely a million to one and greater that as you sinned before you will sin again. Charles H. Spurgeon writes:
If you think about it, God’s value of heaven and yours are very different things. His salvation, when he set a price upon it, was to be brought to men only through the death of his Son. But you think that your good works can win the heaven which Jesus Christ, the Son of God, procured at the cost of his own blood! Do you dare to put your miserable life in comparison with the life of God’s obedient Son, who gave himself even to death? Does it not strike you that you are insulting God? If there is a way to heaven by works, why did he put his dear Son to all that pain and grief? Why the scenes of Gethsemane? Why the tragedy on Golgotha, when the thing could be done so easily another way? You insult the wisdom of God and the love of God.
There is no attribute of God which self-righteousness does not impugn. It debases the eternal perfections which the blessed Savior magnified, in order to exalt the pretensions of the creature which the Almighty spurns as vain and worthless. The trader may barter his gold for your trinkets and glass beads, but if you give all that you have to God it would be utterly rejected. He will bestow the milk and the honey of his mercy without money and without price, but if you come to him trying to bargain for it, it is all over for you; God will not give you choice provisions of his love that you do not know how to appreciate.
The great things you propose to do, these works of yours, what comparison do they bear to the blessing which you hope to obtain? I suppose by these works you hope to obtain the favor of God and procure a place in heaven. What is it, then you propose to offer? What could you bring to God? Would you bring him rivers of oil, or the fat of ten thousand animals? Count up all the treasures that lie beneath the surface of the earth; if you brought them all, what would they be to God? If you could pile up all the gold reaching from the depths of the earth to the highest heavens, what would it be to him? How could all this enrich his coffers or buy your salvation? Can he be affected by anything you do to augment the sum of his happiness, or to increase the glory of his kingdom? If he were hungry he would not tell you. “The cattle upon ten thousand hills are mine,” he says (Psa 50:10). Your goodness may please your fellow-creatures, and your charity may make them grateful, but will God owe anything to you for your gifts, or be in debt to you for your influence? Absurd questions! When you have done everything, what will you be but a poor, unworthy, unprofitable servant? You will not have done what you ought; much less will there be any balance in your favor to make atonement for sin, or to purchase for you an inheritance in the realms of light. (Advice for Seekers)