My dad told me this joke a long time ago.
It is one of my favourites.
I don't exactly remember the little details, but it still works.

One night before bed, a little boy said his prayers.
At the end of his prayers, he ended with:
God bless Mommy.
God bless Daddy.
God bless Grandma.
God bless Grandpa.

His daddy, hearing this was very happy to have such a good son.

The next day, Grandpa had a heart attack and died.
That night, the little boy's daddy heard his son saying his prayers.
He ended them by saying:
God bless Mommy.
God bless Daddy.
God bless Grandma.

The next day, Grandma fell down the stairs and died.
That night, the dad heard his son again finish his prayers.
God bless Mommy.
God bless Daddy.

The dad started thinking, oh crap! Everybody my son is saying God Bless about is dying!!!
The next day, the father had a horrible day! He jumped at every sound and couldn't concentrate on work.
When he got home, his wife greeted him at the door.
He says to her, 'Honey, I have had the worst day!'
She replies, 'You think you had a bad day?! The mailman died on the front steps!!'