If you would like to avoid being idle or unfruitful in the knowledge of our Lord Jesus Christ,
make every effort to supplement your faith with virtue, virtue with knowledge, knowledge with self-control, self-control with endurance, endurance with devotion, devotion with mutual affection, mutual affection with love.
We talk a fair piece about faith and love; virtue and knowledge are also common topics, and self-control (Douay-Rheims has "abstinence") comes up every Lent, at least.
Endurance (DR: "patience") seems like a virtue that would be particularly important to the greenhorn Christians of the First Century, who woke up every day thinking surely today He'd return, then spent their waking hours trying to explain why it wasn't necessary to beat or kill them just because they believed Jesus is Lord.
These days, few Christians, and even fewer Catholics, are het up over exactly when Jesus will return. We are less likely to suffer from naive expectations than from world-weary accommodation. We can fail to endure, not from a lack of patience but from an excess of it, if you will. We get the bumper sticker joke, "Jesus is coming! Look busy," because we know the idleness of those with knowledge of our Lord Jesus Christ.
If I may use another Apostle's metaphor here, we are not in a sprint (as the first Christians thought), but we are in a race (despite the idleness of our own time). Every day until the Last Day, Christians need to endure in their self-control, in the mastery of the spirit over the flesh, if they are to bear fruit for the Master of the Vineyard.