The expressions " Heart " part 1
1. By heart ;
If you know something by heart, you’ve learned it so well you know it from memory
2. To your heart content ;
If you do something to your heart’s content or desire, you do that thing until you are satisfied.
3. Eat your heart out ;
Losing a race that you really, really wanted to win might cause you to eat your heart out, or wallow in grief.
4. Have your mouth in your heart ;
It refers to a heightened state of anxiety or fear. There are many things that might bring your heart all the way up to your mouth,