In plain words
But the thing we get does not stay with us for good. Before we have even enjoyed this joy, it slips away from us. We are parted from that thing. From then on our sorrow begins again. Sorrow until we get it. And when we are parted from what we got, nothing but sorrow. Somewhere in between, while it stays with us for a time, there is joy. Sorrow is greater than joy. Until the thing comes to us, nothing but sorrow. After it has come, nothing but sorrow. What lies between two sorrows is a fleeting pleasure. For such a fleeting, momentary pleasure, we lead our life astray in many ways.
Recognising this very truth, the ancient maharṣis undertook many kinds of sādhana in many ways to hold back this mind. The method of turning the outward senses and the mind inward they called a tantra. They have also called it a mudrā. These mudrās are of five kinds. Khecarī mudrā, bhūcarī mudrā, madhyama mudrā, ṣaṇmukha mudrā and śāmbhavī mudrā. Through these five mudrās they made the effort to turn the senses and the mind inward.
Khecarī mudrā. This comes first of all, and it is very important. When we place our gaze at the point between the two eyebrows, set the mind there too and do dhyāna, the seeing and the seen become one, and we have the chance to experience our own svarūpa. That is, we may keep our eyes open and hold our gaze at the point between the brows. Or we may close our eyes and settle our sight at the point between the brows. But looking at the point between the brows with open eyes is frightening, so we must close our eyes, gather our sight and our mind on the point between the brows, and make the effort to bring this seeing and this seen into one. Practising in this way they called khecarī mudrā.
The second is bhūcarī mudrā. When we place our gaze on the tip of the nose, that is, on the end of the nose, join the mind to this gaze and meditate on God, the Ānanda that belongs to it comes to us. This is called bhūcarī mudrā.