A Slovak proverb says Zdochýnajúca kobyla najviac kope, i.e., The dying mare kicks the hardest.
Naturally, as always with proverbs, its meaning is deeper than an observation about horses.
The idea of the dying mare principle is about humans, both as individuals and as society: Whenever times are changing, those who are about to lose power, control, wealth, or influence, tend to fight hard to preserve the old status quo.
The more they have to lose, the harder they kick. When their demise is inevitable, they often resort to such drastic measures as murder, perhaps feeling if I am going, I'm taking others with me.
For example, in 1989 when most European Communist regimes were already overthrown, the Communist Party of Czechoslovakia instated the hardest line of Communism in the Party's history. In November of that year, people then rebelled and ended their power.
Similarly, toward the end of World War II, Hitler ordered all prisoners of concentration camps executed. If you recall the final scenes of Schindler's List, the Nazi soldiers were supposed to kill all of Schindler's Jews, but Schindler saved them by appealing to the soldiers' humanity. Others were not so lucky.
The mare principle helps us understand certain periods of human history. Its awareness can also help us survive when we happen to live during such periods.