Spiritual understanding is born of harmony between mind and heart. This harmony of mind and heart does not require the mixing up of their functions. It does not imply cross-functioning but cooperative functioning. Their functions are neither identical nor coordinate. Mind and heart
must of course be balanced, but this balance cannot be secured by pitting the mind against the heart or by pitting the heart against the mind. It can be attained not through mechanical tension but through intelligent adjustment. Mind and heart may be said to be balanced when they serve their proper purpose and when they perform their respective functions without erring this way or that. It is only when they are so balanced that there can be true harmony between them. Such harmony of mind and heart is the most important condition of the integral, undivided life of spiritual understanding.
-Discourses 7th Ed p98