When I try to concentrate on my third eye, my point of concentration always tends to move towards the left and disappears. And my eyes are half open automatically. Why?
—Ayushi Agrawal, India
Usually this kind of thing happens due to inner energy moving in a certain way. It sometimes also turns the head or the body. For some reason your energy seems to flow to the left, taking your concentration with it.
Instead, try very consciously not to go with that leftward flow. Try to keep concentrating at the center, between the eyebrows. Insist.
If the eyes open a little, and you are fine with that, it is okay. Half-open works well according to Yogananda. If however it disturbs or distracts you, tell your eyes: “I am the boss!” and keep them closed.
All the best for your meditations,