grieve for someone or something
to mourn for someone or something. Don't grieve for me. I'm okay. She grieved for her lost chances.
grieve over someone or something
to lament and pine for someone or something. Now, don't grieve over a lost cat. There is no reason to continue grieving over him.
What the eye doesn't see, the heart doesn't grieve over.
Prov. You cannot be upset by something you do not know about. When Robbie cracked his mother's favorite vase, he simply turned the cracked side toward the wall. "What the eye doesn't see, the heart doesn't grieve over," he thought.