"And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight: If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister; Who now rejoice in my sufferings for you, and fill up that which is behind of the afflictions of Christ in my flesh
for his body's sake, which is the church: Whereof I am made a minister, according to the dispensation of God which is given to me for you, to fulfil the word of God" - Col. 1:21-25
I've consulted the Orthodox Study Bible, and also the Homily
of St. John Chrysostom on this passage, and I still don't understand the bolded part. What does "and fill up that which is behind of the afflictions of Christ in my flesh for his body's sake" mean?