In this poem the speaker says she is talking about the real heart, not the sentimental image of a heart. Something is wrong with hers. She tries various images to describe it--a "caved hermit," an "unshelled turtle." She listens through an imaginary stethoscope. Most hearts say "I want, I want . . . " but hers is more uncertain. "Duplicitous," she calls it. Her heart says "I want, I don’t want . . . " In the flesh, this heart has an arrhythmia, the speaker can’t depend on it, it causes anxiety. In the spirit, though, this heart is equally undependable. How can she live with it? Sometime she will say "Heart, be still, / and it will."