My heart sank when I opened the letter and realized I had not been accepted into graduate school.
heart sinks
(One) feels disappointed or disheartened. My heart sank when I saw that the meal I'd spent all day preparing had burned in the oven.
your heart ˈsinks
used to say that you suddenly feel sad or depressed about something: My heart sank when I realized I would have to walk home in the rain. OPPOSITE: your heart leaps