Some science behind the scenes
Physically, the heart is the hollow muscle that pumps blood throughout the blood vessels by repeated, rhythmic contractions.
According to many shamanic cultures and older indigenous cultures, however, the heart is the seat of the Lower self [the Subconscious self] - the ‘feminine’ aspect of the Subconscious as opposed to the ‘male’ aspect of the Conscious which is believed to reside in the brain.
Thus whilst the processing of many of the Subconscious activities such as the ability to fantasise, invent or imagine, create, and so on are functions processed by the right brain, the controlling ‘entity’ is in the heart along with one emotion – Love [and hate].
This is why those who know only unrequited love are said to die of a broken heart, and often physically they do.