Grief as Precautionary Tale?

I don't know whether anyone has brought this up before, but since I haven't come across it, I thought I might as well jot it down here...

People have often wondered about the biological function of the kind of deep, lasting grief that accompanies events such as the loss of a child. Why is it so debilitating, and why can it be so debilitating for such a long period of time? Wouldn't it make more biological sense to let the person get on with their life and the business of propagating their genes?

In Stephen Pinker's book How the Mind Works (which would more accurately, but with less impact be called, "An Overview of What We Currently Know About How the Mind Works") he notes that such grief seems to act as a kind of deterrent - basically, knowing how awful it feels acts as a major deterrant to any behavior that might lead to those kinds of circumstances arising.

It occurred to me that perhaps the deterrance is not just for you -- but for those around you, and that this factor could help explain why it is so highly debilitating (if in fact this actually requires any separate explanation). Not only do you experience how awful it is, but others can also see how awful an effect it can have on you. And since in the times when evolution was at work we lived mostly in tribal groups with large numbers of relatives, Kin selection would explain how this kind of grief could evolve to serve "both" these purposes.

Perhaps just the right impact on the grief is where it has a large precautionary effect on the other kin members at the expense of really debilitating the grieving person? (i.e. this is the level of grief that results in greatest chance of those genes propagating, because the least number of people carrying the gene make the mistake that led to the grief).