The concept of time has been around for quite a while. The earliest records of time date back to the 3rd millenium BC with the ancient Egyptian thinker Ptahhotep, who stated, "Do not lessen the time of following desire, for the wasting of time is an abomination to the spirit." The Vedas, early texts on Hindu philosophy dating back to the 2nd millenium BC, also allude to time in describing how the universe undergoes repeated cycles of creation, destruction, and rebirth, with each cycle lasting 4,320,000 years.
Whatever its origins in human history, the nature of time continues to provoke debate to this day. There are two views on the matter. The first view of time states that it is a fundamental part of the universe, an independent entity through which objects "move through" as it "flows" from one event to the next. This view is Newtonian and objective, and most people think about time this way as they go about their day; a major problem with it is that Einstein's remarkably successful theory of relativity does not allow for this view. The second view of time states that it is a creation of the human brain, an intellectual construct used to sequence and compare events. Since this view proposes that time does not really exist outside of the brain, it is subjective; a major problem with it is that despite supportive scientific data, this view of time does not mesh with the "common sense" of most people.
Regardless of whether it really is a fundamental part of the universe or simply a creation of the human brain, we may workably define time as a measure in which events can be ordered from the past through the present and into the future (1). Thus, objective or subjective, time would seem to consist of three components - a past, a present, and a future. The big problem with time is that we don't actually experience the past, which is over, or the future, which has yet to be; in fact, all we can ever really experience is the present - right now.
There is a book called The Power Of Now (2) which contains several points regarding time that are worth considering. In this book, an extremely subjective view of time is adopted by the author, Eckhart Tolle; in fact, he denies the past and future any existence whatsoever, and repeatedly emphasizes the importance of focusing on "the Now":
“Time isn’t precious at all, because it is an illusion. What you perceive as precious is not time but the one point that is out of time: the Now. That is precious indeed. The more you are focused on time - past and future - the more you miss the Now, the most precious thing there is.”
In practical terms, this means that one ought to stop dwelling on the past, and stop ruminating about the future; they are both illusions. While the past used to exist, and the future may yet exist, whatever is happening right now is all that truly exists at any given moment. Therefore according to Tolle, all of one's awareness ought to be concentrated upon the now.
He goes on to say that all things negative stem from one's refusal to acknowledge time as an illusion, and accept things as they are right now:
“All negativity is caused by an accumulation of psychological time and denial of the present. Unease, anxiety, tension, stress, worry - all forms of fear - are caused by too much future, and not enough presence. Guilt, regret, resentment, grievances, sadness, bitterness, and all forms of nonforgiveness are caused by too much past, and not enough presence.”
In practical terms, this second quote adds considerable punch to the initial quote by stating that not only are the past and future illusions, they are also harmful illusions at that - all forms of nonforgiveness result from excessive regretting of the past, and all forms of fear result from excessive worrying about the future. In both cases, awareness of the now is lost, resulting in negativity.
This is powerful stuff, especially for people who tend to think excessively about their past and future and therefore may be suffering from depression or some other malady at least partly as a result of trapping themselves within a cycle of negative thinking. There is no negativity associated with the now - no past so no regrets, no future so no worries - only experience. However, if one is not stuck in such a state of negativity, then perhaps being completely oblivious to the past and future is not always the ideal situation.
The Power Of "Mainly Now"
Probably more than any other animal, humans have been enormously successful in populating the planet and modifying their environment to suit their own needs, a fact that is due in no small part to their their extensive neocortex - that thin, convoluted structure that envelops the rest of the brain. Put simply, the neocortex probably uses stored memories about the past to make predictions about the future (3). Thus, to entirely ignore any thoughts about the past and future really is akin to largely turning one's back on the use of their neocortex, and therefore one of the main tools - perhaps the main one - that distinguishes the human condition from all other things. So by staying in the now at all times, while one can get rid of negativity, they also run the risk of drifting by refusing to steer their ship in the journey of life; never learning never learning from past mistakes, and never using these experiences to make predictions that allow them to better accomplish future goals.
Thus, unless one is immersed in severe negativity, perhaps the best approach is to live mainly in the now, to be aware of what is happening at each and every moment, but to sacrifice a little bit of the now in specific situations so as to actively consider the outcomes of past experiences so as to make better predictions and goals concerning the future. In no way does this diminish the importance of not passively dwelling on past regrets or ruminating about future worries; it is still essential not to do this so as to to avoid negative thinking. Just don't completely ignore the past and future - learn from the former to improve the latter.
Do you allow your mind to wander into past regrets and future worries - thus creating negativity - at the expense of what is happening around you right now?
If you do, try to focus clearly on the now at all times, and stop passively lamenting over past regrets and future worries - these are hurting you.
If you do not, perhaps make some additional time to actively reflect upon past experiences and future goals - and make it constructive.
References (1) http://en.wikipedia.org/wiki/Time. (2) Tolle E. 1997. The Power Of Now. Namaste Publishing. (3) Hawkins J. 2004. On Intelligence. Times Books.