Each moment is fragile and fleeting.
The moment of the past cannot be kept, however beautiful.
The moment of the present cannot be held, however enjoyable.
The moment of the future cannot be caught, however desirable.
The mind is desperate to fix the river in place:
Possessed by ideas of the past, preoccupied with images of the future,
it overlooks the plain truth of the moment.
Those who can quiet the mind
will suddenly discover the path at their feet, and clarity at hand.
Great Middle Way 
When we think of ‘now’ it has already passed.