Referring to the feeling centers of their brain as their "heart." I understand that sometimes heart rate is increased or decreased by emotion, but puh-leez, giving to charity does not mean that you have a "big heart." Giving to charity means that you sympathize with the less fortunate. A big heart? That's called dialated cardiomyopathy and it has a worse prognosis than many cancers.
I sometimes use the stylized heart
emoticon to indicate that I love something, but my understanding stops there.
It's a figure of speech, even though technically your feelings come from your brain and not your heart.