St. Paul actually called Epaphras his beloved “fellow slave” (conservus, σύνδουλος) (Col 1:7), so let us be fellow slaves, too. The slaves of Jesus Christ refuse to budge from his service, even if other masters appear more powerful or more delightful. No. Let us be slaves to the truth, following the truth wherever it leads, even if it is somewhere we might have chosen to go. Let us be slaves to love, surrendering ourselves to it utterly, going wherever love demands.
In this life, firmly saying yes to what is good means firmly saying no to what is bad. If we are to flourish as human beings, we must become slaves to goodness, that is, slaves of Jesus Christ. The more we restrain ourselves from lies, from hatred, from evil, from false Gods, the more we are lifted up from this petty Earth with all its vanities and illusions.
The slavery of Jesus Christ is the grace of God lifting us up to eternal truth. That is why it is said that the yoke of this slavery is easy, and the burden is light.