Though we have constant experience of time, we find it difficult to define.  We quantify time, breaking it down into units which we number (seconds, minutes, hours, etc.)  That is a numbering of motion, of movement of one thing succeeding another.  Time, in this sense, is characterized by uniformity and inevitability.  We call that chronological time  in contrast to psychological time.  Time, in this latter sense, is experienced differently.
Rosalind, the heroine of Shakespeare’s As You Like It, reflected on psychological time.  “Time travels in divers paces with divers people.”   She goes on to list those “who Time ambles withal, who Time trots withal, who Time gallops withal, and who stands still withal.”  Measured by the clock one moment passes just as evenly as any other; but measured by our mind, our conscious experience, an hour can seem but a minute and  a minute can seem like an hour.  Reflecting that conscious experience, a wise old lady remarked,  “It’s not the years that are long; it’s the days.”

We typically think of time as divided into past, present, and future.  Obviously, we can physically live only in the present.  Psychologically, we can live in the past or in the future.  “Past” indicates what no longer exists. We can seek to remedy mistakes of the past but the past is history and cannot be relived.  “Future” speaks of what is not yet. We can plan for the future but the future is mystery and trying to live there is often no more that daydreaming.

Living in the present means being present to yourself here and now; present to the concrete situation in which you find yourself and dealing with that; not constantly looking over your shoulder to the past; not standing on your tiptoes, trying to peer into the future.  And it means being really present to others through respect, care and concern for them.  And you can’t really do that unless you are first present to yourself.

Living in the present is of the greatest importance because it is in the present moment that decisions are made.  And it is the decisions we make, both great and small, that shape our identity and determine our destiny. There is a little verse which illustrates the importance of living in the present.

I have only just a minute.
Only sixty seconds in it.
Forced upon me; can’t refuse it
Didn’t seek it; didn’t choose it.
But it’s up to me to use it.
I must suffer if I lose it
Give account if I abuse it.
Just a tiny little minute,
but eternity is in it.