This is about having to make difficult decisions, and the argument you have between the impulse and fly-by feelings of your heart and the intelligence and rationality of your brain...but the heart almost always wins. When he says, "My brain's the burger and my heart's the coal," he's literally saying his heart cooked his brain. When he says, "My brain's the weak heart and my heart's the long stairs," it's another metaphor about the heart doing in the brain, weakening it, troubling it.
This is about having to make difficult decisions, and the argument you have between the impulse and fly-by feelings of your heart and the intelligence and rationality of your brain...but the heart almost always wins. When he says, "My brain's the burger and my heart's the coal," he's literally saying his heart cooked his brain. When he says, "My brain's the weak heart and my heart's the long stairs," it's another metaphor about the heart doing in the brain, weakening it, troubling it.