Proverbs 5
http://www.biblegateway.com/passage/?book_id=24&chapter=5&version=31

This chapter is an admonition against adultery. The adulteress entices with words that are as smooth as oil from lips that glisten with honey (from verse 3). Appearances are deceptive however, and in the end, the adulteress will leave you with the bitter aftertaste of gall in your mouth (from verse 4). Worse, her snare is a double-edged sword that will destroy both her and her suitor (again, from verse 4). She does not realize that her path is far from the path of life (from verse 6).

Keep away from her and do not put yourself in the path of temptation. I always think that it's interesting that sexual temptation is one of the few temptations mentioned in the Bible that you are not necessarily instructed to overcome; rather, as often as is possible, you are supposed to flee from it and not allow the opportunity to have to confront it to arise. Actually, I find that a little bit scary because it seems to imply that sexual temptation is an order of magnitude greater than the other temptations.

Another Biblical reference to avoiding sexual temptation altogether, from 1 Corinthians 6:18:

18 Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body.

The chapter goes on to outline the havoc wreaked by adultery. It will take away your best years, your years of strength (from verse 9). It will cause your work to profit others and for you to lose your wealth (from verse 10). It will spend your body and your flesh (from verse 11). Rather, pay ear to discipline and be satisfied with the water from your own well (from verses 12 and 15). That will keep your feet from being ensnared by sin, and it will be counted as righteousness to you in the sight of the Lord (from verses 21 and 22).

KEY VERSE:
22 The evil deeds of a wicked man ensnare him;
the cords of his sin hold him fast.