When your son is healthy and happy, you're healthy and happy. And when your son is not healthy, let's say you're unhappy.
If you question your thoughts about when your son is not healthy, you come to see that you're the only one you're worried about. It's like without him, you're not happy - so it's all about your happiness. You want him to live for you - for your happiness.
If something happens to your son, your thoughts about not having him in your life is what your terror is. It's not about his life.
If I'm okay with dying, my son is at least as enlightened as that. If I'm okay with my cancer, my son is at least as enlightened as I am.