God's grace is amazing also because as much as He spends it, it is never spent. His grace is unlimited and His mercy without end. There is something impossible about that. We fear giving things away because we fear we might need it someday. We give but we make sure that we have enough for ourselves. Our giving is not only governed by fear but we give as a people who are sure grace, mercy, kindness, compassion, and even forgiveness are in short supply and must be rationed or we will come up empty. That is part of the reason why it is so difficult for us to be kind and merciful and compassionate -- we treat these are things that need to be protected and preserved rather than given out and given up.
Over and over in Scripture we find this contrast -- the limits and limited things of this world and this mortal life vs the unlimited things of God. So heaven and earth may pass away but the Word of the Lord will not pass away. It is forever. His steadfast love endures forever. His mercy is without end. But the world is already passing away. While we might be tempted to lament the passing of this age, faith leads us to see that this is not the end but the beginning of a new heaven and a new earth and a new life without all that diminishes this heaven, earth, and life and with everything that can only be hinted at here.