As a nurse you work holidays. Easter, Christmas. It's not a nine to five job. It is not a job that allows you to say "eeks it's snowing" guess I won't go to work today.
In fact snow days are the worse days. You show up. It's expected. If you don't the floor runs short staffed. You can't do that, you're a nurse. Nurses work. I recall more than a few times driving on icy, dangerous roads.
Weekends, Sundays, your son's birthday, or your childs school play. Sure, maybe if you're lucky you can convince someone to swap a shift with you. Often you cannot. Because this is nursing, this is the work you do.
Lot's of times you never really thought about how your life and the life of your family would revolve around your shifts. Perhap you would have liked to visit your mom, because it's Mothers Day, but it is your scheduled shift to work. Who wants to swap? Nobody. They too have mothers. This is nursing.