Finally, my brothers, rejoice in the Lord! It is no trouble for me to write the same things to you again, and it is a safeguard for you.
Watch out for those dogs, those men who do evil, those mutilators of the flesh. For it is we who are the circumcision, we who worship by the Spirit of God, who glory in Christ Jesus, and who put no confidence in the flesh--though I myself have reasons for such confidence.
If anyone else thinks he has reasons to put confidence in the flesh, I have more: circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; in regard to the law, a Pharisee; as for zeal, persecuting the church; as for legalistic righteousness, faultless.
But whatever was to my profit I now consider loss for the sake of Christ. What is more, I consider everything a loss compared to the surpassing greatness of knowing Christ Jesus my Lord, for whose sake I have lost all things. I consider them rubbish, that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which is through faith in Christ--the righteousness that comes from God and is by faith. I want to know Christ and the power of his resurrection and the fellowship of sharing in his sufferings, becoming like him in his death, and so, somehow, to attain to the resurrection from the dead.
The "safeguard" comment is interesting. Rejoicing is a safeguard against what? Paul's mentioned it before, so it is important to him that the Philippian church gets the message. He's not impressed by the circumcision crowd, those insisting you need Jesus and circumcision. In Galatians 5:12 he says "As for those agitators, I wish they would go the whole way and emasculate themselves!" Castration was a feature of some ancient religions, Paul may have been referring to that, or he may be just ticked off with them.
By Jewish standards of righteousness, Paul had it all. Ancestry, job, goals, personality. All "a loss," all rubbish.
Paul's new goal is to be like Jesus. The Bible never says "follow Jesus and your life will be a bed of roses" or that we will never be ill, embarrassed, hurt, ignored, poor, hungry, ignored, or anything else unpleasant. Jesus said (John 16:33): "I have told you these things, so that in me you may have peace. In this world you will have trouble. But take heart! I have overcome the world."
So confidence is not based on what happens to us, or Paul would have no confidence at all. Neither is it based on our character, ancestry and what we have done and are doing. Confidence does not immunise us against daily crud showers, but it does seem to be something you can hold onto amid the shower.