The Parsha of "Aishes Yefas To'ar - a woman of beautiful form" is interesting. Often the Torah uses the words "Yefas Mareh - beautiful looking" when describing a woman's beauty, but here only "form" is mentioned. The next few words say: "Ve'chashakta Bah - and you lust for her". A man's lust is usually triggered by a women's "form". It seems that the Torah is introducing to us a Parsha about lust: "What do we do about it - and what results from it?"
Rashi brings Chazal: "The Torah was only speaking 'kineged' the Yetzer Hara". The word 'Kineged' can be understood in two ways. Either "because of" or "against". Interestingly, in this Parsha it seems that both ways are profoundly true!
In the Parsha of Yefas To'ar, Hashem is letting us know that He understands the nature of lust, and that a person cannot always be expected to control themselves. As Rashi says, "if Hashem wouldn't have allowed it, he would marry her even though it was prohibited". And as we saw in last week's Parsha, the people who went to war were Tzadikim who were not afraid of any sin. Even so, we see how powerful lust can be; to the point that Hashem knows that he would sin if it wasn't permitted. This is the simple understanding of the word "kineged" - meaning "because of". In other words, the Heter (permission) of Yefas To'ar was given "because of" the powerful nature of lust.
However, the other meaning of the word "Kineged" means "against". In this case, Chazal can be understood as saying the following: "Why did the Torah write the Parsha of Yefas To'ar? To teach us how to work AGAINST the Yetzer Hara".
Hashem knows that lust can be super-powerful. We can't always just say "no" to the Yetzer Hara and walk away from an over-powering feeling of lust. So what hope is there for us in such a situation? Comes this Parsha - in Hashem's infinite wisdom, and tells us what to do in such a case. If we can't just walk away, here's what we CAN do instead: "Vahaveisah el toch beisecha" - Take her into your home, but... WAIT. Don't give in to the lust right away. "Vigilcha es roisha" - Let's shave off her long flowing hair, cut off her pretty nails, we'll dress her up in clothes of mourning, etc... Hair, nails and clothing all represent the "chitzonius" i.e. the "outer trappings" that don't let us see the real person underneath... Ok, now we can start to see her for who she really is; a bald, weepy eyed woman, dressed in shmatehs.
And we can do the same thing if we saw someone and feel overpowered with lust. If we feel unable to just let go of it, we can take the image inside our mind - but instead of relishing it, we should imagine that we shaved off her hair and nails, and dressed her in rags! Then, there is finally hope that we'll let go of the lust.
And if we still don't want to let go of it and insist on arousing the lust in spite of the fact that it has already cooled down, then the end will be bitter. As Rashi writes, he will come to hate her; i.e. he will end up hating the lust. He will have a Ben Sorer U'moreh from it... meaning - perhaps, that the end result (alluded to in the idea of "his son") of purposefully arousing lust, can be a complete rebellion against Hashem.
What we can learn from all this, is how to work kineged the Yetzer Hara when we feel overpowered with lust. Instead of trying to fight it, we can say to the Yetzer Hara: "you know, you're right. This really looks good. But let me look into it just a little closer... What is this women that I desire really made out of? As our Sages have said: "a barrel filled with excrement, her mouth is filled with blood"... Let me have a look at some of the pictures in the Last Resort Tip #11 on this page before I give in to this overpowering feeling of lust...
And like "Pintale Yid" once posted on the forum:
I was walking home several weeks ago from a Shabbos simcha, when as a result of having to pick up my head to look at the color of the street light, I saw something that that I didn't want to see and it threw me for a loop. I saw that I was losing the battle so "in my mind", I invited myself to follow the "frum" lady home. When she took off her high heels, as a result of those treifa heels, I saw the most ugly bruises on the heels of her feet and I imagined that her feet stunk worse then the dorm rooms in yeshiva. I also try to imagine her as if she was a walking skeleton.
I think this is the deeper meaning of that Gemorah where if you are at the mercy of something you saw, then take it in and modify it to where you are totally disgusted by it. The Gemorah uses more "base" turnoffs, and each person can imagine the levels that work for you. Isha Chavis Melei'ah Tzoah...