Day 5 Sutra 1:3 Then the Seer (Self) abides in His own nature.
What's in it for you, when the mind is still? Patanjali says that when your mind isn't filled with fluctuating thoughts and desires, then self-realisation is there. Oneness with yourself is there. You are your true self.
We tend to identify with our body, mind and energies as if they are the self.
When the mind is chattering you tend to be emotionally, mentally and physically engaged in what you are seeing or doing or hearing or smelling or touching. However, when the mind is still, only your true self is there and you know and perceive only your true self, which is the “eternal peaceful You.”
When the modification of the mind are there, the fluctuating thoughts are there, it's like looking in one of those mirrors you get at amusement parks which distort your image – you can look thin, wide, wavy, etc. (Thoughts do a similar thing). Then when you look in a 'normal' mirror, you see what you consider to be your real undistorted reflection.
I've had the experience of being in my living room, with the TV on, and with my attention on a deep, deep, deep peacefulness within me. It was like being an endless well of calm and peace. No thoughts were there. It's hard to put into words but the peace felt alive and pulsating. I was aware of the sounds from the TV. I looked at it, but I was not engaged with it.
So, as I contemplate the meaning of this Sutras at my personal level, that experience was like abiding in my own nature and seeing/feeling, may be just an aspect of, my true eternal self or original state.
Thoughts were not there. Just the peace.
Sri Swami Satchidananda puts it this way: “You are the Knower or Seer. You always see your mind and body acting in front of you. You know that the mind creates thoughts; it distinguishes and desires. The Seer knows that but is not involved in it”