The author of the book The Power of Now is Eckhart Tolle. The questions here can come is if I am not my thoughts then what am I? Who am I? This is the beginning of self-awareness, self-inquiry, and mindfulness.
Lesson 1: You are not your mind
You are not your mind, you are not your thoughts is quite a bold statement. The problem of humanity is deeply rooted in the mind itself. The mind is an incredibly useful tool but we have become identified with it. We believe that the stream of thoughts is who we are but we are actually much more than that.
Practice the below
What you can do is step back and observes your thoughts instead of being wrapped up in the stream of thoughts. Be there as the witnessing presence of your thoughts, and do so without judgments.
Then take note of what your mind is doing. When you become better at observing your thoughts you will feel a deeper presence behind the thought. This way you have disidentified yourself from the thought stream. After a long enough practice, you will eventually experience a gap between thoughts known as “No Mind”.
No Mind is the opposite state of mind. You are more aware, alert, and fully present in the moment.
The moment your attention turns to the now. You feel a presence, a stillness, a peace. You no longer depend on the future for fulfillment and satisfaction – you don’t look to it for salvation
Lesson 2: The present moment is all we will ever have, so live in the here
Listen to your mind for 10 minutes and see for yourself what it is saying. Now is all there is. The mind is always trying to escape the now since it has no power here. The mind needs the past and the future memory and anticipation to exist. It hides from the present. It lives in the past and creates a story for itself or it wants to look towards the future for some kind of fulfillment.
What is missing at the moment?
The answer is nothing. All these wants, desires, and regrets come from mind obsession with the past and future.
Lesson 3: Acceptance of what is
Your resistance creates pain. So do not resist. Be aware. There are no problems, only situations to be dealt with now, or to be left alone and accepted as part of the presence of the moment until they change or can be dealt with.
Accept the Now as it is!
You cannot suffer from the past or future because they do not exist. What you are suffering are your memory and your imagination.