Guarding Against Sexual Sin by Wilhelmus a Brakel

Everyone ought to be on guard so that, consistent with the exhortation of the apostle, everyone may possess his vessel in sanctification and honor (1 Thess 4:4).

1. We must know that we have the enemy within ourselves, that we carry the seed of uncleanness within, which will very readily shoot up if we do not carefully watch against this. Happy is he who has a true heart of a virgin, for when this sin takes hold, it cannot very easily be driven out. Therefore, watch!
2. Carefully avoid all occasions which would stimulate this sin—be it via the eye or the ear. One must therefore watch very carefully over these two senses. “I made a covenant with mine eyes; why then should I think upon a maid” (Job 31:1).
3. If an unclean motion arises in your heart, immediately shake it off as you would shake off fire from your clothes. Divert your thoughts immediately to something else. Here, fleeing is the best option. If, however, you do not reject the initial thought and you allow your thoughts but to reflect on it for a moment, you are conquered. This sin will flourish rapidly and will at once exercise great power.
4. Be always engaged in honest activities. Even when you are free from obligations, do not let your flesh be idle. Arouse yourself to be engaged in your task with delight and earnestness, so that it may occupy your heart, and thus there will be neither room nor time for this filthiness.
5. Be moderate in eating, drinking, and sleeping, for if there is a lack of moderation in these things, the body will be vulnerable for this sin and the lust for and yearning after this sin will arise that much easier.
6. Avoid such people who are inclined toward this sin—be it that they are giving license to the flesh or that they are battling this sin. There can very easily be a word or something else which ignites a virgin heart. Furthermore, this sin will take hold all the more readily if one also is battling against this sin himself.
7. Arm yourself with fear for God‘s presence and omniscience. Pray continually: “Create in me a clean heart, O God.” If it is common for this sin to frequently assault you, have days of fasting for this—and the Lord will help the person who is engaged in this battle.
8. Always consider the consequences of this sin. It yields but a brief delight for the flesh and a long and bitter aftertaste for the soul. And if this aftertaste presents itself as a lively reality for you, you will then be able to reject its brief delight that much easier.