The letter to the church in Philadelphia: This church in Philadelphia is the second of the two churches in Revelation with no correction needed. It is not suffering as badly as the church in Smyrna. Rather, it is healthy and so it provides a good example for us.
The letter to the church in Sardis: Revivals are never born out of indifference, complacency, lethargy, and superficial forms of religion. Revivals are born out of repentance, brokenness, spiritual poverty, and a passionate longing for God.
Every Christian’s life has a spiritual trajectory. The same can be said of churches. The church in Thyatira had a serious problem which we certainly want to avoid, but the best compliment that Jesus pays them may well be that their last works are more than their first. That is the course we want our lives to follow.
In Pergamos persecution had already taken the life of one member of the church. The threats now had substance. The outward situation was precarious, but Jesus sees a greater danger for this church rising from within.