The gospel comforts us by reassuring us that we can give because God will always give us more. Giving as gospel then focuses not on what we fail to supply for God, but on what God will supply to us. In other words, the gospel says that God gives to you so that you can be generous with your money and yet live without the worry that you won't have enough. While the law focuses on giving from our own limited resources, the gospel focuses on our giving from God's unlimited supply of resources given to us for this very purpose. This is a significant shift in perspective.
Most people see their money and possessions as their own.
This is law thinking because it imagines that we are responsible for our own financial success and monetary blessings. Gospel thinking realizes that we may be the ones who labor and work, but God's grace is still responsible for all the wealth that comes our way. Therefore we don't worry about giving some of that wealth away because God is able to give us still more. The law-oriented view thinks we must bless ourselves, jealously hoarding and guarding our wealth. The gospel-oriented view gives wealth away realizing that God has unlimited resources with which to give back to us.