Galatians 5:11 talks about the "scandal of the Cross". What's the scandal of the Cross? It's that the Son of God died for sinful and wicked creatures. Why's that a scandal? Because it cuts to the heart of men and women: it proves to us that there's nothing we can do to earn God's approval. Men and women are so utterly and completely lost, nothing short of the death of God's Son could help them.
"[I]f righteousness [is] by law, then Christ has died for nothing" (Galatians 2:21). Man's inability to impress God is summed up in the Cross: if God wants to have communion with women and men, He has to act sovereignly. He has to act with no regard to their merit. If God wants to accept men and women, He has to introduce the death of Christ.
There is no basis for God to accept us, except that Christ died for us.
But the Cross doesn't only tell us we needed Christ to die so we could live. It also tells us that the life we had in ourselves has ended. "I am crucified with Christ" (Galatians 2:20). I was so bad, that I needed to be crucified. There was nothing in that life that God could work with, so He ended it in Christ, and gave me Christ for my life (Colossians 3:1–4).
The Cross is scandalous, because it teaches me that even now I can't impress God in the flesh.
This was the error of the Galatians: they wanted to make a "fair appearance in [the] flesh" (Galatians 6:12). They want to "boast in your flesh" (Galatians 6:13). What is the Apostle's opinion of this? "[F]ar be it from me to boast save in the cross of our Lord Jesus Christ" (Galatians 6:14).
So much of our Christian lives is spent in a vain attempt to make a fair appearance in the flesh. Why? Because we really hate the scandal of the Cross. Because we find it so hard to believe that "in me, that is, in my flesh, good does not dwell" (Romans 7:18). Because we refuse to accept God's reckoning of ourselves.
The Scriptural answer is not to improve ourselves. The Scriptural answer is a complete change of focus. There's nothing wrong with boasting, but there's only one thing we can boast in. "[F]ar be it from me to boast save in the cross of our Lord Jesus Christ, through whom [the] world is crucified to me, and I to the world" (Galatians 6:14).