The feeling of looking into a significant other's eyes, recognizing that the relationship you are engaged in with this person is ending, and realizing that in all probability the significant other is thinking the same thought, and then engaging in said sex in a, perhaps slightly detached initially, but eventually generally passionate, sex act.
I knew that we were going to break up after we had our first doom sex after only a month and a half of dating. It just wasn't going to work
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