Maybe speaking from the middle of your heart is better.
When someone screams “At the top of their lungs” it means they’re screaming as loud as they can. Yet, when a person says something from “The bottom of their heart” it means they’re being very deeply truthful and meaningful. So which is it? Is the top or bottom the most powerful part of something in your chest? Personally, I think it would make more sense to say you’re screaming “From the bottom of your lungs.” That would imply you’re getting as much air and power from the lungs as you can. To scream from the TOP implies you’re getting the bare minimum of strength into the scream. I don’t know how this ever even became a saying. This is a dumb saying and I mean that from the “Top of my heart.” See how stupid that sounds? Hearts and lungs aren’t the same thing, but they are neighbors and close friends. I think we can agree their bottoms are more important than their tops.