Sick at heart
Definition 1 of 1
Pro Tip 1/3Emotional Weight
The phrase carries a heavy emotional load, suggesting deep sadness or disappointment. 
After the team's loss, the fans were sick at heart.
Pro Tip 2/3Metaphorical Use
It's a metaphor indicating emotional pain, not physical illness. 
Despite his smile, he was sick at heart over the breakup.
Pro Tip 3/3Intensity of Feeling
Use it to describe intense feelings, more than just being a little sad or upset. 
She felt sick at heart knowing the old tree would be cut down.