6 Now what does this mean, my beloved, but that we also, when the enemies are arrayed against us, should glory in afflictions, and that when we are persecuted, we should not be discouraged, but should the rather press after the crown of the high calling in Christ Jesus our Lord? And that being insulted, we should not be disturbed, but should give our cheek to the smiter, and bow the shoulder? For the lovers of pleasure and the lovers of enmity are tried, as says the blessed Apostle James, 'when they are drawn away by their own lusts and enticed.'
But let us, knowing that we suffer for the truth, and that those who deny the Lord smite and persecute us, 'count it all joy, my brethren,' according to the words of James, 'when we fall into trials of various temptations, knowing that the trial of our faith works patience. ' Let us rejoice as we keep the feast, my brethren, knowing that our salvation is ordered in the time of affliction. For our Saviour did not redeem us by inactivity, but by suffering for us He abolished death. And respecting this, He intimidated to us before, saying, 'In the world you shall have tribulation.' But He did not say this to every man, but to those who diligently and faithfully perform good service to Him, knowing beforehand, that they should be persecuted who would live godly toward Him.
Source: Letters (New Advent)