Hebrews 8:13
10 Many of you have often beheld the Olympic games: and not only have beheld but have been zealous partisans and admirers of the combatants, one of this [combatant], one of that. You know then that both during the days of the contests, and during those nights, all night long the herald thinks of nothing else, has no other anxiety, than that the combatant should not disgrace himself when he goes forth. For those who sit by the trumpeter admonish him not to speak to any one, that he may not spend his breath and get laughed at.
If therefore he who is about to strive before men, uses such forethought, much more will it befit us to be continually thoughtful, and careful, since our whole life is a contest. Let every night then be a vigil, and let us be careful that when we go out in the day we do not make ourselves ridiculous. And would it were only making ourselves ridiculous. But now the Judge of the contest is seated on the right hand of the Father, hearkening diligently that we utter not any false note, anything out of tune.
For He is not the Judge of actions only, but of words also. Let us keep our vigil, beloved; we also have those that are eager for our success, if we will. Near each one of us Angels are sitting; and yet we snore through the whole night. And would it were only this. But many do even many licentious things, some indeed going to the very brothels, and others making their own houses places of whoredom by taking courtesans there. Yes most certainly. For is it not so? They care well for their contest.
Others are drunken and speak amiss; others make an uproar. Others keep evil vigil through the night weaving, and worse than those who sleep, schemes of deceit; others by calculating usury; others by bruising themselves with cares, and doing anything rather than what is suited to the contest. Wherefore, I exhort you, let us lay aside all [other] things, and look to one only, how we may obtain the prize, [how we may] be crowned with the Chaplet; let us do all by which we shall be able to attain to the promised blessings. Which may we all attain in Christ Jesus our Lord, with whom to the Father and also to the Holy Ghost be glory, might, honor, now and for ever and world without end. Amen.
Source: Homilies on the Epistle to the Hebrews (New Advent)