Sforno on Genesis 3:15/ספורנו על בראשית ג׳:ט״ו

1ואיבה אשית, woman would henceforth be an object of disgust even in her own estimation, as described in the Talmud (Shabbat 152) “although a woman is a vessel full of excrement and her orifice full of blood,” (men run after her as if she was the most desirable creature) This was going to be the relationship between males and females in the future, not only that between Adam and Chavah [who apparently could not bring himself to have intercourse with her for the next 130 years. Ed.]

2ובין זרעך ובין זרעה, not only between Adam and Chavah, but also between their respective male and female offspring.

3הוא ישופך ראש, these thoughts crossing man’s mind will reduce the satisfaction he obtains already in the early stages of sexual intercourse, a feeling gradually reinforced when he considers the potential harm he may cause himself by indulging in copulation, diminishing both the qualitative and quantitative enjoyment of it.

4ואתה תשופנו עקב, he who initially derives pleasure from his superiority will eventually cause himself harm at the end of the pleasure cycle.