Sob your heart out
Definition 1 of 1
Pro Tip 1/3Emotional Intensity
Expresses profound sadness, often due to a significant loss or great disappointment. 
When he heard the bad news, he just collapsed and sobbed his heart out.
Pro Tip 2/3Not for Everyday
Used in situations of deep emotional pain, not for minor upsets or everyday disappointments. 
She didn't sob her heart out over a spilt coffee; it's too extreme for such small issues.
Pro Tip 3/3Informal Expression
Generally used in more casual conversations among friends or family, not in formal settings. 
In a support group, he felt safe to sob his heart out among friends.