I have a question.....?

Why do women cry during or just after sex? Is it just and emotional thing where you let yourself go, or is it so good that you just cry and cum. This is an on going thing with my fiance and I. This afternoon, after working a full 8 hours overtime, plus the hour plus ride home, I got a little surprise when I walked in the door. A few Cabo Wabo's later, I was behind her, doggie and I heard her start to cry. She said that things where fine, and it was just dam good sex......So what is it ladies. Dam good sex or things under the surface.