Before Paul’s readers came to Christ, they were involved in many shameful behaviors. They didn’t deserve Jesus’ salvation, but it was given to them as a gift. The Gentiles or non-Jews were especially distant from God because of their worship of other gods, but now both Jews and Gentiles can come to God in the same way through Jesus.
Maybe you can relate to Paul’s description of wrong behaviors before coming to Christ. Even people who lived pretty good lives before Jesus can recognize they have come a long way. It’s another reason we can be thankful for Jesus’ role in our lives. We can take note of things we used to be and do and be glad they are in our past.