For the entire law is fulfilled in keeping this one command: “Love your neighbor as yourself."
There are different ways to use the Golden Rule. Making decisions based on whether you would want it "done unto you" is only one of them. Galatians 5:14 goes beyond putting yourself in the shoes of another. The spark of God resides in you. When you love your neighbor as yourself, you are bringing them closer to God. In every action there is a reaction. Bring someone closer to God and you become closer to God too.