The heart was created with a very particular nature and for a very particular purpose. When you fail to use any created thing for the purpose in which it was created, it breaks. 

The heart was created by and for God. The heart was created to know and love God. The heart was created to be given to God. 

The heart that is given to or filled by any other thing suffers the most painful impoverishment and death. 

The human heart that allows this dunya to enter it breaks and drowns and becomes owned by this life.