My husband and I have always taught our children to find the good in everything, even if they can’t see it at that moment.

But I was still surprised when I found a plastic baggie in my elder son Brayden’s room a few weeks before Halloween. He’d scribbled “$ for MD Andrson” on it and put a dollar bill and a few pennies inside. When I asked him about it, Brayden said he was collecting money he’d found on the ground or gotten from...