13. As to the flight of dangerous occasions, St. Philip
Neri used to say that cowards that is, they who fly
from the occasions gain the victory. Hence you must,
in the first place, keep a restraint on the eyes, and must
abstain from looking at young females. Otherwise, says
St. Thomas, you can scarcely avoid the sin. "Luxuria
vitari vix protest nisi vitatur aspectus mulieris pulchrae."
(S. Thom. 1, 2, qu. 167, a. 2.) Hence Job said : " I
made a covenant with my eyes, that I would not so much
as think upon a virgin" (xxxi. 1). He was afraid to
look at a virgin ; because from looks it is easy to pass to
desires, and from desires to acts. St. Francis de Sales
used to say, that to look at a woman does not do so
much evil as to look at her a second time. If the devil
has not gained a victory the first, he will gain the second
time. And if it be necessary to abstain from looking at
females, it is much more necessary to avoid conversation
with them. "Tarry not among women." (Eccl. xlii. 12.)
We should be persuaded that, in avoiding occasions of
this sin, no caution can be too great. Hence we must
be always fearful, and fly from them. "A wise man
feareth and declineth from evil ; a fool is confident."
(Prov. xiv. 16.) A wise man is timid, and flies away;
a fool is confident, and falls.
--St. Alphonsus, Sermon on Impurity
http://www.archive.org/stream/sermonsforallsun00liguuoft/sermonsforallsun00liguuoft_djvu.txt
Sermon on bad thoughts:
Above all, in order to avoid bad thoughts, men must abstain from looking at women,
and females must be careful not to look at men.
I repeat the words of Job which I have frequently quoted: I made a
covenant with my eyes that I should not so much as think upon a virgin.
he says that he made a covenant with his eyes that he would not think.
What have the eyes to do with thinking? The eyes do not think; the mind
alone thinks. But he had just reason to say that he made a covenant
with his eyes that he would not think on women; for St. Bernard says
that through the eyes the darts of impure love, which kills the soul,
enter into the mind." Hence the Holy Ghost says: Turn away thy face
from a woman dressed up. It is always dangerous
to look at young persons elegantly dressed; and to look at them
purposely, and without a just cause, is, at least, a venial sin.