The equinox is a twice-yearly, worldwide event. Because of the way the earth axis of rotation tilts, on these two days each year the days and nights are almost equal everywhere in the world.
This balance between day and night is most notable at the extremes, the north and south geographic poles. Near the equator the days and nights are roughly equal in length year-round.
Balance is something we do not think about or act upon enough, perhaps because so much balancing is done automatically. We humans learn balance as infants and graduate from crawling to walking. Most animals are quicker at the skill, learning to walk within minutes or at most hours of birth.
Our bodies are full of balanced biochemical dances, insuring that there is the right amount of salt, oxygen, sugar, amino acid, in fact just about everything, in our blood. In our cells proteins and other simple and complex molecules are constantly created and destroyed in order to keep the right balance and get the cells' job done.
Out of balance means sickness and death.
In the world at large there must be a balance between predators, herbivores, and the plants the herbivores eat. Too many predators is bad even for predators; too many herbivores is bad even for herbivores.
The mind, too, is best when balanced. To have an unbalanced mind is to be insane, to be helpless or even harmful to society.
Balance can also be a mere point of transition. The fall equinox gives way to the cold of winter (in the northern hemisphere); the spring equinox to the heat of summer. A little oscillation may be built into all sorts of systems, biological and cultural as well as physical. We might say such a system is balanced if it is within its normal range of variation.
It appears that the human population of the earth has gotten out of balance. The prime culprits are medicine and agricultural improvements, which we normally think of as good things. Perhaps the balance of nature has permanently changed. More likely at some point our human population will swing back to either its old normal or a new normal.
Human life is a tricky thing. The most difficult of all, I think, is to keep an ethical balance. The world is filled with incentives to stray from an ethical course. Ethics is largely the matter of treating people fairly, which sometimes means giving up some self-interest. But giving up too much self-interest means allowing, even encouraging, others to take advantage of you, and of others. Such generalizations are easy to make, but many situations may not be easily to fit into this general picture.
Balance. Not too fast, not too slow. Not too calm, not too nervous. I think it might be a nice place to be.