In her latest seasonal video as part of Kensington Palace's quarterly Mother Nature series, Kate also describes it as a season of "deeper connection".
The princess launched the series in the northern spring as a celebration of the changing seasons.
On Instagram Kate described autumn as "a season of reflection, growth and deeper connection. Embrace the beauty found in change, as we prepare for winter's rest. C"
Filming for the video took place in Northern Ireland, which the princess visited with the Prince of Wales in October, including at Long Meadow Cider in Co Armagh and Mallon Farm in Co Tyrone.
"As the days grow shorter and the shadows grow longer, the energy of summer withdraws into autumn. This is a season for reflection and refinement," Kate said.
"Trees shed their canopies in preparation for winter, just as we too learn to let go of what is no longer needed.
"Through greater awareness of our inner and outer worlds, we can find clarity and purpose in what matters most, encouraging us to simply pay attention and listen.
"Mother Nature teaches us there is beauty to be found in change, impermanence and in letting go. These are the natural cycles of life," she said.
"Whilst the blossoms fall and the colours fade, the roots grow deeper. Stronger.
"Let love be the root that holds us, the light that guides us, with hope, through change. Endure."
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