I'm always scared that my period will come at the worst time... And usually it does. Going swimming later? Not anymore. Going on a long ass road trip? I'm going to be in pain now for the whole darn thing.
It's like my uterus knows when I'm going to be doing something fun and just decides that it's the perfect time for me to bleed.
I suppose this isn't a fear, I'm just always worried that my period will come at exactly the wrong time.