I think we have all felt this to be true, even if we experience it as an urge to do spring cleaning, to travel, or to stay near home. Many people still feel September is the start of the new year, no matter how long they've been out of school. Ancient people were aware of these cycles of the cosmos, and were aware of being a part of this phenomenon themselves, biologically, emotionally, and spiritually. They honored the seasons of change taking place inside as well as outside, knowing them to be the same. To me it speaks of having magic, to be aware and in awe of the eternal creation going on around us, and within us.
Autumn is the time of harvest.
It is a time to gather up the fruits of our labors, to give thanks for our bounty, and to prepare for the winter to come. The Autumnal Equinox is also the time of balance between light and dark. It is when the Sun passes our equator. It is a time to prepare for the descent into the darkness. The ancient Celts interpreted this transfer of light to dark, as they did all dramatic changes in the Earth and Sky, both literally and figuratively.