Why Solstice is used for spiritual growth?

Earlier today was the winter solstice. This moment of the year, as well as the summer solstice and both equinoxes are treasured by spiritually aware persons. I had heard about that for some years, but it was not until this year that I learned more about why. In the video of today a reflection on this. 

It is a rather new topic for me, and for that please don´t stay with the literally expressed words but take the direction that I am describing. In terms of terminology, I am learning on this - and it is part of the journey that I share here.  If you follow the journey longer, you will be updated with adjustments, more profound backgrounds etc. After recording this spontaneous video I listened again to the Sadhguru video that I refer to and had listened to months ago (https://youtu.be/bL_QRa7uoXY ). He reflects on the equinox and not on solstice with the balanced energies.    

As common happened, I innocently thought it was the same. Despite mixing between equinox and solstice, the four moments have a similar silent moment in the year that one can actively take advantage of. In this older video from Sadhguru, he is reflecting on the window created at solstices: https://youtu.be/g_3enLcoDMc.  

With the intention of combining the empowering "tools" of the solstice, meditation and leycentra, I meditated in a small chapel at older trees later in the day. For sure next equinox and soltices I´ll be more prepared and take even advantage of the natural peaceful moment to empower the positive evolution. How about you?