“..with the affection of Christ…”
How is it that Paul claimed to love people with the affection of Christ? There is this exchange of my own pain for His. So Paul is in prison, writing about fellowshipping with Christ suffering.
Most of us are fellowshipping with our own suffering. The way to tell, is when we get hit, we hit back. But Paul was fellowshipping with Christ’s emotional life. So he was able to say that he loved others with Christ’s affection. There had been that exchange which is required to enter spiritual maturity, when one gives God their own pain and enters more and more of His.