He's not behaving like she was that important to him! Or better say, the author trivialise something very important to her and her culture, for a joke, to make him quirky, first by sleeping during her efforts and later kissing her like he it was not something that was important to both of them in (his) past! By saying, honestly "I'm sorry, don't know what came over me, I got carried by the moment!" would made the situation less cringy, imo!