A certain situation has happened again and again in my gaming experience. One player interprets a rule one way ("He gets a 5+ save!"), while the other player interprets it another way ("No, he gets a 2+ save!"). The more these two players argue and make an issue over it, the more likely the eventual die roll will make both interpretations irrelevant. (the actual die roll in the example above will almost certainly be a 1 or a 6. As the discussion gets longer and more heated, the probability of this occurring approaches 1)
More succinctly, the more you argue over a particular rules interpretation or how to handle a given situation, the less it will matter because the point will end up being moot.
This is known as "The Inverse Law of Arguments Mattering", or the "Law of Your Pants".
It is described by the equation:
U = Importance of the point of contention to the game as a whole
R = Relevance of the point of contention to the game as a whole
p = number of players involved in argument
a = anger level generated
n = number of rulebooks consulted
t = length of time the point is argued
s = stupidity of the whole situation
A corollary to this is that the more effort you exert in winning the argument, the less of an impact your little victory will have on the game. (For example: You argue vociferously that your character gets a cover save against that meltagun, only to have him killed 2 seconds later by a laspistol shot from the same attacking unit)