Sentimentality is emotion for emotion’s sake. And that’s bad. Good art, a good story or book or song or movie will offer an experience that engages us as a whole person. When Christians are sentimental we are compromising the Gospel.
Nothing is innocent because of the Fall, and our return to innocence comes at a significant cost. Christian author Flannery O’Connor says that Christian sentimentality is a result of separating Nature and Grace, and when we do this, Grace is degraded to pious cliché, and Nature becomes either sentimental or obscene.
We can avoid sentimentalism and pious cliché by seeing the physical world everywhere infused with the transcendent and the so-called spiritual things as grounded in the stuff of life.
But it’s so hard to do this in our culture—we’ve been brought up with the separation.