Question for Deepak:
How can I help a friend who has lost a child?
After such a tremendous emotional wound as losing a child, it is normal to grieve and go through some depression. As the friend of someone who has suffered such a loss, your job is not to provide insight or make them feel better.
Understanding and insight does heal, but it has to come from within that person who is suffering.
More than being intellectual, this understanding has to be emotional, spiritual, and psychological. All you need to do is continue loving and supporting your friend to support their natural healing process.
There are many good books that offer guidance in understanding mourning. In general, you want to be able to help your friend accept the truth of their loss and why it hurts so much, so they can know themselves, fully trust their feelings and have faith in themselves once more.