Murphy's Laws ... 

FIRST:    Nothing is as easy as it looks. 

SECOND:   Everything takes longer than you think. 

THIRD:    In any field of endeavor, anything that can go wrong will go wrong. 

FOURTH:   If there is a possibility that several things can go wrong,
          then the one that will cause the greatest damage will be the one to go wrong. 

FIFTH:    If anything absolutely can NOT go wrong, it will anyway. 
SIXTH:    If you perceive that there are four possible ways in which a procedure 
          can go wrong and circumvent these, then a fifth way, unprepared for, will promptly develop. 

SEVETH:   Left to themselves, things tend to go from bad to worse. 

EIGHTH:   If everything seems to be going well, you have obviously overlooked something. 

NINTH:    Nature always sides with the hidden flaw. 

TENTH:    Mother Nature is a "son-of-a-gun." 

ELEVENTH: It is impossible to make anything foolproof, because fools are so very ingenious. 

TWELTH:   Things get worse under pressure.