Understand your heart first

And if so, then do the sayings like “I love you with all my heart” and “my heart swelled with joy” mean something or are they just poetic language?

The heart, as basically as one can describe, is an electromechanical pump.

An interview with Dr Suresh Venkita - Medical Doctor and Chief Physician from Pacific International Hospital in Port Moresby, explains that the heart surely feels but in response to the brain.