"It does not depend, therefore, on man's desire or effort, but on God's mercy." (Romans 9:16)
I have a lot of trouble wrapping my head around the idea of mercy, and worse, the truth that I depend on it, really. Mercy conflicts with my sense of agency and responsibility. Don't I have to do it myself? do it right?
But the answer is, simply: No. All I have to do is believe ("This is the work of God, to believe in the one he sent"), and God's mercy takes care of the rest. Believing is work, yes, and real belief does translate into action. But the thing everything else hinges on, balances on, turns on, dangles from: depends on: is mercy.
Mercy is the sun and the soil and the water, and I am the plant, just growing.