For freedom Christ has set us free; stand firm therefore, and do not submit again to a yoke of slavery.
I think that the concept of freedom is a difficult one for those of us in the west to understand. Slavery has been abolished for a long time, and I believe we truly have a heard time grasping what it means to be a slave and what it means to be free. When we think of freedom, it is freedom from responsibility, like winning the lottery. That is not the kind of self-centered freedom the Bible speaks of. When a slave is set free, his life changes. What he used to depend on for his daily sustenance is now gone. The harsh master is no more, but the slave is now free to live a life based on what he chooses. In today's economy, that could be quite rough! Freedom carries responsibility, perhaps even more responsibility than being a slave. But, rather than depend on a harsh and cruel master, true freedom empowers one to experience a joy that they could not know under such a master. It is for the sake of such freedom that Christ sets us free.
So why go back? That is the very point of the book of Galatians! Why go back to living under the law when Christ frees up from the cruelty of the law. Not that we have an absolute freedom to live as we please, but now we choose to obey in response to what Christ has done for us.
In slavery, not all master were cruel. Some only had one or two slaves, and chose to treat them with some dignity. Some of these slaves chose to remain with such masters. They continued to serve, even though they could leave. Perhaps their daily lives did not look much different, except that where they once had no choice and lived in fear, they now had a choice and could live in freedom. And perhaps some, out of the sheer joy of having a good master, now put their hearts into their responsibilities, and worked harder than before. That is where turning the other cheek comes from, going the extra mile. Why? Because we are free. Free to live and love in a way that we did not know was possible. Free to surrender to God because He is the only way, the truth, and the life. I couldn't earn my way to God under the law, but my life now is a response to the freedom I find in knowing that I don't have to, that the debt has been paid. Praise God!