Little could he have imagined then that Sara's death would lead to his starting an inspirational program to help young cancer patients cope with their disease and the pain that accompanies it.
"She went through the most painful things," the rabbi told The Early Show co-anchor Julie Chen, "and she'd pat me on the back and say, 'It's OK, Daddy. I love you.' So she definitely was our inspiration and continues to be our inspiration."
Cancer treatments can make children weak. Chemotherapy, especially, can greatly upset small stomachs.
The man who's come to be known as "Rabbi G" left the synagogue for the hospital and became one of the most unlikely "action heroes" the kids will ever meet.
The rabbi remembered, "I walked up to this little boy and I said, 'You know, I'm a black belt.' And his eyes bugged out. To a little child, that's really a big deal. And I said, 'Do you want me to teach you some karate?' And he almost jumped off the table. When the nurse took the needle out 20 minutes later, he looked up at her and he said, 'Did you do it yet?'
"He felt nothing?" Chen asked.
"That's when Kids Kicking Cancer was born," the rabbi says.
Children who are frightened and screaming while undergoing a painful medical procedure are often held down even tighter to get it over with faster, Chen notes. But what Kids Kicking Cancer does is teach these kids that they are in control of their disease; that, through the martial arts, they hold all the power.
Kids Kicking Cancer began five years ago in Detroit, and has since expanded to New York-Presbyterian Children's Hospital.
The rabbi says they hold one-hour classes every Tuesday. They "begin with a body scan ... and we look for any place of nausea, of anger, fear, of tightness, of stress, just let it fall."
Taking the class has helped Diana Garcia cut back on the painkillers she was taking after surgery: "They really helped me, like, they meditate with me, and tried to calm the pain down. And they did."
"We've had kids who are on active morphine, who ask the nurses to unhook them so they can go the karate class, then come back and they don't need (the morphine)," the rabbi relates.
Angela Greene says her 5-year-old daughter Shakayla is learning to cope with fear, and takes her lessons home with her: "She learns courage, and that it's OK to be afraid, but we have to do what we have to do. And she's learned that."
The children get awards belts, celebrating their newfound power over the invisible enemy they face every day.
Siblings also learn to cope with their brother's or sister's cancer.
Shakira O'Neill's sister Julissa is a patient. "It was sadness, real sad when I heard about her. I was crying and everything. But I still love her," says Shakira, who comes to class each week with Julissa.
"(The class) makes me braver," Julissa says.
"Some of the kids won't go into the hospital without their uniforms ... and the doctors are telling us that this is creating a revolution in how they are approaching pediatrics," the rabbi says.
He ends each class with the words, "Power. Peace. And purpose." Words that have special meaning from Julissa and Shakira.
"I tell her that you don't have to be sad because I'm always your sister and I'll never forget it," Julissa says.
Rabbi Goldberg's dream is to expand the Kids Kicking Cancer program nationwide.