The use of biofeedback data is becoming increasingly popular in interactive art and design, acting as a mirror of the self. It opens up interesting avenues for facilitating technology-mediated self-reflection on the body. However it also poses challenges for interaction design, given the semi-involuntary nature of control we have over our physiological data and the personal and social implications of externalising what is normally invisible. We describe the case of Eloquent Robes, an interactive installation, aiming to elicit self-reflective engagement with personal physiological data that normally remains concealed from our everyday awareness. The study explored methods for facilitating the subjective interpretation of heartbeat data represented in an artistic form, as an aesthetic revelation of the inner self during a moment outside the quotidian. Participants were asked to compare their results with other people's manifestations in the form of a reflective garment, revealing a mirroring of the self in the other. Heartbeat - as a physiological data - might not be an accurate tool for prediction of another person's feelings, however when shared as a metaphor of feelings, it can be an effective tool for the generation of narratives and self-revelation. We contribute a set of design strategies for interactive biofeedback artworks that aim to address some of the challenges of using physiological data as an aesthetic resource to enhance bodily self-awareness.