They were quite capable of using a word literally, and they were also quite capable of using a word as a metaphor. The overwhelming majority of places where the Bible uses the Hebrew word leb or its Greek equivalent, kardia , it's used metaphorically. And the heart, in this metaphorical usage, has an incredible variety of uses. Hearts can be glad . Hearts can be troubled .
Hearts can be fearful , or courageous .
Hearts can fail, melt, tremble, grow hot , grow sick , and do lots of other things. When we talk in English about the heart, we see it as the seat of feelings and emotions . Even in English, though, our emotions move around a lot. You've also heard people say that their hear was in their shoes, or that their heart fell into their boots. Didn't know it moved around that much.