cry heart out

cry (one's) heart out

To cry for an extended period of time. Poor Jane really cried her heart out during the funeral service. I can't watch those sappy movies because I just cry my heart out every time.
See also: cry, heart, out
Farlex Dictionary of Idioms.

cry one's heart out

 and sing one's heart out; play one's heart out; sob one's heart out
Fig. to do something with vigor or intensity. She suffered such grief—alone and sobbing her heart out. The bird sang its little heart out each morning.
See also: cry, heart, out
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • cry (one's) heart out
  • cry your heart out
  • cry eyes out
  • cry
  • cry (one's) eyes out
  • cry one's eyes out
  • cry your eyes out
  • cry like a baby
  • a cry from the heart
  • cry from the heart