I like what you say about the valley. It reminds me of the space between breaths. One thing that I have found quite helpful for calming my mind is to focus my concentration on the area of my heart. In my experience, and also from my practice and studies, I have found that there is a palpable strong-gentle-calm energy that emanates from the heart, and I can calm myself considerably just by resting my mind there. Also, by shifting focus to the heart, energy is drawn down from the conceptual mind. It is this ungrounded energy that is responsible for over-thinking, and by focusing on the heart the energy is brought down to the true mind! The energy that arises from the heart is also much different than emotional energy. I suppose one way to describe it is as if it has a cooling effect rather than the firey effect of the emotions. It is calmer, quieter, and more subtle, although also far more powerful! Give it a try and let me know if you notice any difference.