In DBT they teach about the emotional mind and the logical mind. Maybe the emotional mind is analogous to the heart in this discussion. Either of the above can get you into trouble if you operate from logic alone or emotions alone. Then there is a balance that you can strive for, the "wise mind." So, the way I interpret this is that there are parts of the mind (or heart) that might keep us ill, but that also have a lot to offer us. When we balance those parts and get them to work together, then we are healthier.