Idioms for unhappiness:
1. Down in the mouth
When you look down in the mouth you look depressed and unhappy.
E. g. You’re looking down in the mouth. What’s the problem?
2. Feeling blue or to have the blues
To feel (or look) blue is to feel (or look) depressed or unhappy.
E. g. I’m feeling blue today.
3. Beside yourself with grief / worry
When you are beside yourself with grief or worry your feelings are so strong that you are overwhelmed by them.
E. g. They were beside themselves with grief when their mother died.
4. Reduced to tears
When someone or something reduces you to tears, they make you feel so unhappy that you cry.
E. g. My boss reduced me to tears when he shouted at me.
5. Downhearted
If you feel downhearted you feel sad or depressed.
E. g. Don’t be downhearted. You can retake your exams next month.
6. Heartbroken
If someone is heartbroken they are feeling intense and overwhelming sadness.
E. g. We were heartbroken when our old dog died.