The unreal never is; The real never is not. The truth about both has been seen by the knowers of the Truth (or the seers of the Essence).
— Bhagavad Gita 2.17
The unreal never is. The unreal was, the unreal would be, but the unreal never is.
The past and the future does not exist outside of our minds. What you think as past is nothing but stored up memories. What you think as past is nothing more than your own account of what happened. It can never be an accurate account of what actually happened. Even if you think it’s accurate, it exists only in your mind right now. It is not real. The past never is. You have the present, the reality in front of you right now, so why worry about the past? There is no reason to worry about the past, and there is no reason to bask in the glory thinking about some good that has happened to you in the past. It is no more.
Similarly, what you think as future is only your own imagination of what would happen, it has not happened yet. The future never is. The future is unreal. There is no reason to fear about something that might happen the future, because there is every chance your fears won’t come true, and you are only spoiling your present with your unnecessary and unpleasant imaginations. Likewise, there is no reason to be excited about something good that might happen in the future because there is every chance what you anticipate won’t happen, and by getting excited you take your focus away from the present and you are only heading towards disappointment.
Reality is now. This is the truth. Be real. Be in the now.