Maybe backing himself up and removing his hand from Eve's waist was the best idea logically, because otherwise an embarrassing, er, morning effect would have become painfully obvious to her. As it was, Jack still felt as if it was the wrong move. Somehow.
A quick glance over his shoulder at the clock, as he sat up and pulled one leg up to disguise his current...situation, revealed the time. "Wow, actually almost not-morning." When he turned back around, and both saw and heard Eve's reaction (mental replays were lovely like that), something unsettling (ironically) settled into his stomach. The grin that had been growing on his face faded somewhat.