It happened that way with a girlfriend back before I was married. We met at the after party to a Christmas event, exchanged numbers, went on a dinner date. We went out again three nights later, and fell into deep lust with each other, and I was head over heels about her after that. By Valentines Day we were moving to very serious. But about the time I was going to ask her to marry me, she was getting commitment jitters, and broke it off.
We dated off and on for another year and a half. And I wondered about her for a long time, even after I got married to someone else.