Some parents try to be miners, when they should be farmers.

Some parents try to be farmers, but find it too slow.

Some parents “do unto others what was done unto them.”  They are neither miners nor farmers -- they are assassins.

Assassin parents scope-in on the little faults and pull the trigger.  Failure is an opportunity to pull the trigger.  Childhood is awful when living with assassins because the child is the always-present target for nasty bullets of constant criticism. 

Criticism has its place, just like rifles have their place.  Used improperly, both can be deadly.