You've heard of Murphy's Law, Everything that can go wrong will... at the worst possible time and in the worst possible way. There are other related Laws: 

** After your hands become coated with grease, your nose will begin to itch. 
--Lorenz's Law of Mechanical Repair 

** Identical parts aren't. 
--Beach's Law 

** Any tool, when dropped, will roll to the least accessible corner. 
--Anthony's Law of the Workshop 

** Nothing is as inevitable as a mistake whose time has come. 
-- Tussman's Law 

** If it jams, force it. If it breaks, it needed replacing anyway. 
--Lowery's Law 

** The solution to a problem changes the problem. 
--Peer's Law 

** There is no mechanical problem so difficult that it cannot be solved by brute strength and ignorance. 
--William's Law 

** Machines should work. People should think. 
--IBM's Pollyanna Principle 

** The most ineffective workers shall be moved systematically to the place where they can do the least damage. 
--The Dilbert Principle 

** The first rule of intelligent tinkering is to save all the parts. 
--Ehrlich's Law 

** It is a mistake to allow any mechanical object to realize that you are in a hurry. 
--Ralph's Observation 

** If you tell the boss you were late for work because you had a flat tire, the next morning you will have a flat tire. 
-- Cannon's Comment 

** The newer the carpet the greater the likelihood that the bread will land jelly side down. 
-- Law of inevitable consequences.