Suffering has a sanctifying purpose; it humbles, kills pride and undue self-confidence, gives spiritual perspective and chases us to Christ for sustaining grace. Very often it is only in hindsight that we realize the cathartic effects of suffering and praise God for the experience.
Suffering manifests and magnifies in our life what has happened in our union with Christ and what is symbolized in baptism; “we have been crucified with Christ,” have “died to sin” and have risen again with Him in newness of life (Galatians 2:20 cf. Romans 6:1-3).
Peter’s little phrase “suffered in the flesh” ties together very well the theology and the circumstantial reality. He who has experienced the harsh realities of life and suffered in Christ, has died to self, “cease[s] from sin” and is moving towards holiness. Furthermore, Peter said, when we suffer, we should arm ourselves with this thought; that Christ has died for us, therefore we, who are in Christ, should be ready to die to self as He did.