The historian and essayist Pamela Haag has written a whole book about marriages like Danica and Stefan’s, which she calls “melancholy marriages.” Analyzing the plight of these “semi-happy couples,” she explains:

A marriage adds things to your life, and it also takes things away. Constancy kills joy; joy kills security; security kills desire; desire kills stability; stability kills lust. Something gives; some part of you recedes. It’s something you can live without, or it’s not. And maybe it’s hard to know before the marriage which part of the self is expendable . . . and which is part of your spirit.