The sinfulness of man and the goodness of God
When evil takes root in society, Christians face persecution. To avoid this, some will conform. Jesus warns against this: We must be willing to be persecuted for doing what is right. At the same time, we must not return evil for evil, but rather do good and show mercy.
One of the joys of parenthood is pride when our kids achieve great success. Paul's 'kids' - believers in Christ in Thessalonica, were a source of pride to him: They stood strong despite persecution. And as a result, they would be 'counted worthy of the kingdom of God.'
Paul's epistles are so upbeat and optimistic, we forget that he faced constant opposition and discouragement in ministry. The Christians in Thessalonica suffered persecution, too, so Paul shared secrets of joy in the midst of trials. These are valuable lessons for us today.