It brings to mind another proverb 'the ENDS justify the MEANS' and I fell that 'all is fair in love & war' is a little too glib. To start with War, or rather the act of making war has absolutely nothing to do with fairness. To establish rules or guidelines for war, the Geneva Convention for example, is certainly noble in theory but in practice rules simply give an advantage to the side that chooses to forgo their use, over the side that follows them. War is only a struggle for supremacy, it is not a game, and the only real use that rules serve in war is to give that war a civilized appearance to hide what is in-fact a bloody mess of weapons, violence, terror, and collateral damage. There is nothing fair about war, take for example the animosity felt towards our Soldiers for the deaths of Iraqi Women & Children. It is a travesty to be sure, but this animosity seldom extents all the way to the insurgents who hide themselves among the Women & Children for the specific purpose of creating anti-war sentiment in the U.S when our media shows pictures of these innocents caught in the cross-fire. It has nothing to do with fair or unfair, it is simply a matter of strategy & tactics. The only way to civilize war, to make it “fair”, would be to abolish it entirely.
The matter of fairness in LOVE however is much more complicated. I have often marveled at the fact that a loved one, so cherished, can so fast become a hated enemy. This is because a lover is far more capable of hurting you deeply than others. To love, really love, someone is the strongest anyone can ever feel for another. People often go to great lengths to gain it and then again to keep it. I would never steal a friends money, or car, but I have stolen a friends Girlfriend which probably hurt worse than any of the former ever could. When it comes to love I feel that fairness applies the same as in any other human relations, but for love we will often break these rules. Love can make us do stupid things, especially regarding ‘break-ups’ when this love is threatened. Petty jealousy, paranoia, rage, & violence can all be the final result of love. Love is unfair just as war is unfair and both can bless or ruin lives, I am not sure where the proverb came from but it is a clever & rather general way to describe two very complicated matters.