Your heart is the corridor between your soul and your mind.
The joy in your soul must move through your heart, otherwise it will "not even enter your mind."
Feelings are the language of the soul.
They will back up in your heart if you have a closed mind.
Open your mind, allow your feelings to be expressed, to be pushed out, and your heart will neither break nor burst, but be a free-flowing channel of the life energy in your soul.