In 1950, the young son of Robert Marcus died of polio. Albert Einstein wrote this short metaphysical exposition to help him through the pain. Is it philosophically sound? I don't know. But when someone is mourning the loss of a child, that's not really important.
Read a transcript at Letters of Note.
Link
I worked as a hospital chaplain one summer. One day, I was called upon to baptize a dead baby. Did it help the baby? No. But it helped the mother a lot.
What I do believe is that saying there is some sort of life after death is delusional.
As far as I'm concerned there is nothing after death.
If that is too harsh for you just accept that we don't know. Why is this so hard to deal with for some people? And it gives yourself the possibility to mourn instead of believing we go to heaven, in which case we should celebrate death instead.