17 Now therefore let us return to that, wherefore we have said what we have. We have need of Continence, and we know it to be a divine gift, that our heart fall not away unto evil words, to make excuses in sins. But what sin is there but that we have need of Continence, to restrain it from being committed, since it is this very Continence which, in case it have been committed, restrains it from being defended by wicked pride? Universally therefore we have need of Continence, in order to turn away from evil.
But to do good seems to pertain to another virtue, that is, to righteousness. This the sacred Psalm admonishes us, where we read, “Turn away from evil, and do good.” But with what end we do this, it adds bye and bye, saying, “Seek peace, and ensue it.” For we shall then have perfect peace, when, our nature cleaving inseparably to its Creator, we shall have nothing of ourselves opposed to ourselves. This our Saviour also Himself would have us to understand, so far as seems to me when He said, “Let your loins be girt, and your lamps burning.” What is it, to gird the loins?
To restrain lusts, which is the work of continence. But to have lamps burning is to shine and glow with good works, which is the work of righteousness. Nor was He here silent with what end we do these things, adding and saying, “And you like men waiting for their Lord, when He comes from the marriage.” But, when He shall have come, He will reward us, who have kept ourselves from those things which lust, and have done those things which charity has bidden us: that we may reign in His perfect and eternal peace, without any strife of evil, and with the highest delight of good.
Source: On Continence (New Advent)