My theory is that everything about a successful civilization comes down to impulse control: when you are angry, how well can you control your impulses? When you are emotional, how easily can you return to work?
Note that this has nothing, necessarily, to do with individual self-control: a successful civilization could control its people's destructive impulses through fear or through constant gratification.
But I think the most pleasant societies are those where, though the government does not actively coerce you to control your impulses, the people of the country controlled their impulses fairly well, because not doing lead to an assured death.
I argue that different races have different levels of impulse control because different ways of life demand different levels of impulse control, which are then evolutionarily selected for. A farmer must be able to control himself pretty regularly in order to yield enough crops to survive for the winter. Those who cannot think 9 months ahead, in other words, and then plan and act accordingly, simply did not live long enough to pass on their genes. Leading to many stable farming societies where murder and crime rates are low.
I wish there was some world-wide measurement of impulse control, behavior and planning. But I can't find that. However, IQ is close enough.
Without a doubt, the asians seem to have the highest impulse control of any society, which is no surprise since most of them were farmers.
On the other side of the scale is the spectrum is the negro, who has barely made it into an agrarian lifestyle, and shows a tendency to anger and crime ("crime" of course is relative; in a tribal, hunter-gatherer setting, such low impulse control is not necessarily maladaptive and in fact could be beneficial).
I also think the weather plays a primary role in determining how well a people learns to weed out those with poor impulse control and planning skills. Obviously those who must survive harsh winters must think farther.