Ki Teitze תרל”ב 1

במדרש לוית חן הם המצות מלוין האדם כו’.
The Midrash quoting the pasuk in Mishlei (1:9) “The (mitzvot) are a beautiful wreath (לוית) for your head” The word לוית can also mean to accompany.
שיש בכל דבר מצוה שיוכל האדם לדבק הכל ע”י המצות להש”י.
For in every mitza one does, one can connect everything to HaShem
לא דיברה תורה אלא נגד יצה”ר.
Rashi says that the reason why one is allowed to marry this captive woman is because the Torah knows that had it not been allowed, people would anyway transgress this sin, and therefore it is allowed.
והלא ביד הקב”ה לעזור לאדם נגדו או שלא יסיתנו ולמה הי’ הצורך להתיר איסור.
But why is this so? HaShem could have made one not have a desire in the first place, why should something forbidden be allowed? (see above תרל”א)
רק שזה עצה להתיר דבר שמושך האדם לרע
The answer is, that this is indeed a way to release a person from the desire to do evil
שע”ש זה נק’ איסור כמ”ש בסה”ק שע”י נאסר האדם ונקשר לרע.
This is why it is called אסור forbidden, which can also mean tied up. Because through doing sins, a person becomes tied up drawn to do something forbidden and then connected to the bad
רק עי”ז שגומר בדעתו שאם לא התירה הכתו’ לא הי’ נושאה.
Only because of this heter in the Torah, that the Torah said this is allowed, and the person is no longer trapped in the Yetzer hara. Therefore he decides in his mind that had it been forbidden I would not do such a thing. (He has a more objective perspective, because there is no enticement he can see it for it is)
עי”ז נעשה היתר שלא להיות נקשר ונאסר ע”י לסט”א ואם הי’ איסור לא הי’ יכול לגבור נגד היצה”ר
Through this it becomes allowed היתר or untied, or disconnected. That he is no longer connected to the Yetzer Hara, because had is still been forbidden, he would not be able to overcome the yetzer hara, for he would be confused by the enticement
רק עתה בנקל יותר לברר לעצמו שאם הי’ אסורה לא הי’ נושאה.
Now however it’s much easier for him to say that had it been forbidden he would not have done it
ועצה זו נוהגת בכל דברי רשות שצריכין שמירה שלא להתדבק בהם ע”י שמברר לעצמו שאם לא הי’ רצון הקב”ה להתנהג בעניני עוה”ז לא הי’ עושהו כנ”ל:
This advice can be applied to any worldly thing that a person has to do that’s not a mitzva (work etc.), that needs special protection not to get too drawn after it. That if a person decides that if this is not the will of HaShem I will not do it, so he automatically doesn’t get dragged into the physicality of it.