Is there a limit to how much grace God will give? I think the people of God could debate this for a long time. It could be a more productive argument than that of eternal salvation being guaranteed or losable. I think these kind of dialectic conversations can help open up our hearts and keep us from running to extremes. "It is good to grasp the one and not let go of the other. Whoever fears God will avoid all extremes." (Eccl. 7:18)
Is God's grace scarce, or in short supply? There's a good list of extrememes to avoid before the above quote in Ecclesiastes 7. One is being over righteous. Are you tense? Angry? Scared? When I am, I rarely admit it. Once I'm over or through it, then I'm more open to talking about it. But what is the medicine that helps me get over what ails me? It's not more anger or fear. That just shuts me down or makes me run in other ways.
The medicine is grace. Like a lot of elixirs or antidote, it has to be used in the right way and correct dosage. Using it everyday just because it feels good would be like continuing to take morphine years after the pain from the surgery was over. Like the wrong use of chemicals, I would argue it is possible to abuse grace. That doesn't mean God is short on grace, or runs out of it. But like a doctor He might change treatments, When we stop responding to grace or abusing it, He might need to use some of the other tools in the box.
Truth and Law are also valuable tools in the hands of God to heal and set us on the right path. Because some people might abuse grace, should I never use it? That would make about as much sense as not taking the antidote for poisoning because too much of it could kill me. Well not taking the right dose of the antidote of a snake bite is equally fatal.
Grace through faith in Jesus is the antidote to Sin and its wages, Death. Jesus came "full of grace and truth", and was also the fulfillment of the Law. He obeyed it all so we don't have to and will never be good enough. Jesus is good so we don't have to. But once we taste His pleasure, he gives us the desire and ability to please God, because we want to.
We'll never be perfect in this body and world, but by God's truth and grace we can be sure of perfection in eternity. In the mean time let's make sure we use grace without losing sight of truth. The Good News Translation states the same truth slightly differently: "Avoid both extremes. If you have reverence for God, you will be successful anyway."