In verse 6, Paul points us to what really matters - faith working through love. Paul points us repeatedly to faith and Christ's work as the sole basis for our salvation. This is absolutely true. However, this emphasis on faith is not meant to point us away from the effort that results from that faith. A faith that is real will actually do something. Paul says that our faith works through love.
One key phrase that I want us to remember is "grace-driven effort." Grace-driven effort is our response to God's love toward us. God has shown us His grace, and we respond with our will and effort BECAUSE of what He has done for us. We do not obey the commands of God IN ORDER TO GET His love. We obey because we already have God's love. I understand that this can be a difficult distinction to discern. However, honesty before the Spirit and others with our motives will show us what is true in our hearts.
Verse 12 is a humorous/figurative approach to understanding the works and faith tension. Paul says that if really believe that are outward actions are the basis for our justification, why in the world would be stop at mere circumcision? Paul says that those leading the Galatian church astray should go all the way and "emasculate themselves." Frankly, Paul says that they should cut it all off. (Don't get mad at me, it's in the Bible!)
Again, I ask you to consider what you are pointing to as your defense before God. It is absolutely anything other than Jesus? Are you pressing into Christ, and Christ alone as the basis for your hope? When things go wrong in your life, to whom or to what do you run? Jesus, and Jesus alone can provide hope, satisfaction, peace, comfort, and ultimately, salvation.