Memento mori : A memento mori (Latin 'remember that you must die') is an artistic or symbolic reminder of the inevitability of death. "The expression 'memento mori' developed with the growth of Christianity, which emphasized Heaven, Hell, and salvation of the soul in the afterlife."
My main character being a cleaner and atheist, memento mori has for her the first meaning. A constant reminder that life is a fragile thing that can stop suddenly from one moment to another. So she don't fear it, it's a completely normal thing like breathing in her eyes. But that doesn't mean she has a death wish, she only aware of it, that's all.
I would like to develop more, but I would end up writing a full thesis of the subject and it could spoil some point of my story !