Romans 9:16
So then it depends not on human will or exertion, but on God, who has mercy.
Human Effort
Human Effort Has a Ceiling
Through human effort and strength, a good high jumper can leap to about seven and a half feet. But the pole vaulter is different. He carries a pole that he fixes into a hole in the ground. He puts all of his trust in that pole not only to hold him, but to lift him higher than he could ever go on his own. In fact, he may go three times as high as the high jumper.