“If God, in his forbearance, tolerates us when we serve sin,” said a wise elder, “how much more will His mercy strengthen us, when we struggle for what is good.”
God tolerates our sin, I believe, because God gave us free will and God respects us enough to allow us to choose whatever we will. We see the effects of the exercise of our free will all over the place. We are destroying the planet, for example. People choose to be ruled by fear or prejudice. People chose to do evil and people chose to do good, love their neighbors, and to love and enjoy God.
However, when we chose to do good, God is all over that, giving us what we need to continue to choose good because choosing good is a moment by moment existential experience. We are free to stop choosing the good in every moment of our lives.