The Anna Karenina Principle
the one thing that distinguishes happy people from unhappy people, is that happy people place happiness as their highest priority whereas unhappy people have different highest priorities like fame, wealth, power, justice, deference, honor and the list just goes on and on...
Perhaps this is what Tolstoy meant in Anna Karenina when he said that:
"All happy families are alike; each unhappy family is unhappy in its own way." I was surprised to find that this quote has given its name to a social science rule; the Anna Karenina Principal which states (from Wikipedia):
"that a deficiency in any one of a number of factors dooms an endeavor to failure. Consequently, a successful endeavor (subject to this principle) is one where every possible deficiency has been avoided."
In other words, there are countless reasons why a family can be unhappy whereas all happy families have have the common trait of avoiding these factors. It sadly follows from the Karenina Principal that happy families are rare and unhappy families are common. Like George Carlin said "Last night, I had dinner at a family restaurant; there was an argument at every table"
It also explains why the dog, as a pet, has no real competition, save for the cat (turn and spit on the floor) which runs a distant second. The reality is that if your cat were the size of a Great Dane, it would attempt to eat you (or kill you for sport) without a moment's hesitation.
The dog is one of the few animals which does not have any major dis-qualifiers which place it out of the running as a pet. Elephants may be just as sweet and loyal as a dog but their size presents an insurmountable deficiency. Virtually all other animals, which possess all or some of the beneficial pet oriented traits of a dog, possess some other major disqualifying trait.
Sadly, most martial strife occurs because one mate accepts a dis-qualifying trait in the other, with the expectation that they will be able to remove the trait. I'm not convinced that this is a necessarily an unrealistic expectation. But while habits are trainable, personalities are not.