Anything fun has the potential to end in disaster, and as a parent, I seem programmed to foresee that disaster in graphic detail.
Leaving toys of the floor? You’ll trip over them later.
Climbing a tree? Watch you don’t fall. Remember The Boy Who Lost An Eye Like That.
Washing your hands before dinner? Mind the water’s not too hot.
Not washing your hands before dinner? You’ll catch a bug and make yourself ill. Then you’ll give the not-washing-hands-bug to your mother and me. We will be so ill that we won’t be able to take you to your friend’s party at the weekend.
Is that what you want? Because that’s what’ll happen.
Update 7/08/2009: DJ Bogtrotter has found the gravestones.
Matt Edgar writes here 
This reminded my of this (the 1st one):
http://www.steph-angel.com/blog/?p=525
P.S. This is an excellent blog & thanks for the link. Is it OK if I link to you too?
Hi, thanks for the comment – like the Calvin and Hobbes. Fine to link here! Regards, Matt