Celebrating this; links us to nature's cycles and a deeper connection to our own cycles, the balancing of darkness and light, the power of letting go, and the acknowledgement that everything changes.
Tantra as a spiritual practice is always ultimately about Oneness and the skilful use of polarities like Shiva and Shakti - or consciousness and energy. It is tempting to put the two together and think in terms of a harmonious balance of Shiva and Shakti. This can be misleading. Putting together two different types of qualities can cause more problems than doing so may solve. The familiar yin yang symbol of a black and white sector whirling together has limitations but it is better than mixing black and white together and getting grey!
This is true even with the Equinox as a balance of light and darkness. They are not exact opposites - one candle will dispel the darkness, but one bit of darkness doesn't remove all light.... On a planetary level from the perspective of space there isn't day and night just a beautiful blue-green planet spinning in space.
Whatever the equinox means to you, may you be blessed, may you be loved, and may you be held gently in this golden autumn light.