My ex I am sure felt very vulnerable when I started realizing something was wrong with her and she didn't have a backup supply. She begged me she didnt want to breakup. So i didn't. But the whole time she was online looking for a backup when she found one she told me to go ahead and move on and didnt blink an eye. So the only time I think they feel vulnerable is when they r about to lose their supply source and dont have a backup.