"I want you to know, brothers, that what has happened to me has really served to advance the gospel, so that it has become known throughout the whole imperial guard and to all the rest that my imprisonment is for Christ. And most of the brothers, having become confident in the Lord by my imprisonment, are much more bold to speak the word without fear. Some indeed preach Christ from envy and rivalry, but others from good will. The latter do it out of love, knowing that I am put here for the defense of the gospel." - Philippians 1:12-16 ESV
Paul was in prison but he knew that he was 'put' there. The Greek word used is keimai (Strong's G2749) for the apologia (Strong's G627) of the Gospel. He was aware of his location but He was more aware of God in his location.
This passage precedes the above passage.
"And it is my prayer that your love may abound more and more, with knowledge and all discernment, so that you may approve what is excellent, and so be pure and blameless for the day of Christ, filled with the fruit of righteousness that comes through Jesus Christ, to the glory and praise of God." - Philippians 1:9-11 ESV
Pure blameless thinking involves an awareness of placement. When we are aware that God functions in grace and has us where we are in grace then we are free from accusation and we have a redemptive expectation.
We are placed where we are and others are going to do what they do but we are there to be a living explanation of grace until God puts us somewhere else.
Paul was in prison but he was approving what is excellent because he had his eyes on Jesus.