We all have a past; some of us may have a pleasant one, while others a less pleasant one. No matter what, the past was gone, and no longer real, except the memory of it. Only the present is real, and that is why it is called "present" -- a gift or present from the Creator.
Letting go of the past may hold the key to living a stress-free life. It is the wisdom of living well in this day and age. In this material world, many of us believe that more is always better. Why do we want more? The explanation is simple: we tend to identify all material things with our ego: the car we drive, the house we live in, the clothes we wear, the career we have. But they are all in our minds, and they don't last. Knowing this ultimate truth, we still hold on to everything in our possession, refusing to let go. This is how we have created stress in our lives.
Life is about mind over matter. To fully harness your mind power, first of all, you need to fully understand the role of the mind and how your mind works, so that it may work for you, instead of against you; and then learn the strategies to fully utilize your mind power. You think and your thoughts become the raw materials with which you weave the fabrics of your life, including your choices and decisions, your actions and reactions; your thinking is based on your perceptions of your past experiences, and the memories of those experiences.
According to Lao Tzu, an empty mind means you let go of all your memories that are responsible for inflating your ego. Without your ego, you have no stress.