Here Paul is urging the church to believe in what God has done for them and is continuing to do in them. That God is bringing them deeper into righteousness, and that, at the same time, that righteousness is their inheritance as Children of God. That nothing they do can earn it, that it is something God works in them, with them, through faith.
Righteousness in God is achieved by faith, by believing that we are children of God because of what He has done for us. Believing that in partnering with God he is bringing us deeper and deeper into righteousness by his grace rather than by our ability. Paul is exhorting the church of Galatia to believe they are in this position towards God. That it is one of faith and dependence, rather than one that works to be righteous. There is no level of “enough” you can do to earn righteousness. When Paul references circumcision here, he is more so referring to the old ways of Judaism; living under the law and achieving righteousness by the works of the law. He is pointing out that that is no longer the way of living they are called to. That because of Christ, they don’t live under a system that asks them to achieve their place in Christ by works, but one that is achieved to by faith in what Christ has done.
Our culture is one centered on performance. We see this in the way our social media is built, likes, approval, getting a yes from everyone around you that what you are doing is cool, good, w/e. We have learned it in school, sports and it isn't necessarily bad! In fact, in many cases it's good. It becomes bad when we live our lives by it. When we are making choices based on the approval of others. Often, we bring that way of living into our relationship with God.
A lot of times we believe that we have to "do do do" for Him to love us, or invite us in. Which is not true. What we are actually doing when we have that approach to God is pretty dishonoring. We are taking the position that Jesus dying on the cross for us wasn't enough- that we have to do a bit more to be accepted by God, and it will really distort your relationship with Him. Because then you approach Him from a slave-master type of way when He didn't actually want that. He wants you as a daughter or a son, as a friend, as someone He co-labors with. Approaching God as a good and loving Father also frees you up to be open and honest with Him and enables you to do good works out of a desire to please Him, rather than to earn His love (which is freely given).
a practical step
In what areas of life do you need to believe you are already a daughter, already a son? Do you fully believe God's love for you, his bringing you into His family is done by Him and not something you can earn?
Pray this, "Father, thank you for your wild love towards me. Thank you that you have made a way for me to be in relationship with you. Thank you that you are calling me into deeper righteousness and freedom, and that you are co-laboring with me, working in me to see me there. I ask that you would reveal to me your love and acceptance of me. God please show me any area where I am striving for your love that is already freely given to me. I lay down all my attempts at your affection and I as fully as I know how receive your love. Come and encounter me today. I love you, Amen."