One of the things that characterizes people who are trying to earn God’s favor by following rules is to be proud of their success at keeping rules and critical of people who don’t. Paul turns that around and tells the spiritual ones to be humble and gently help those who are failing. He closes out the book with some advice about supporting those who are their teachers, and demonstrates that the letter is actually from him by closing it in his own handwriting. Paul probably had poor eyesight and had someone else write his words down in writing most of the letter.
A sad thing about moving forward in our relationship with Jesus is that it can cause us to see more clearly the failings of those around us. Those who have truly been led by the Spirit in their relationship with Jesus react with compassion, like Jesus did. Those who are just following rules react with judgment. We all react the wrong way sometimes, but that should cause us to turn to the Holy Spirit for guidance.