Horace advises that we seize the day. "Life ebbs as I speak: so seize each day, and grant the next no credit." The trouble with this advice is that what we are told to grab is so deficient in entity as to be barely seizable. The admonition comes almost to this: seize the unseizable, fix the flux, stay the surge, catch the wind.
I do indeed try to seize the day, and its offerings, day by day, moment by moment. Walking along the trail I stab my staff into the ground saying "This is it, this is your life, right here, right now, and it is good." Living in tune with this mantram, without wanting to be elsewhere or elsewhen, is obviously better than standing on tiptoes trying to make out the future or looking through memory's rear-view mirror.
There is no full living without presence to the present, without mindfulness to the moment. But mindfulness is ultimately no solution since what one is minding is ultimately empty.
The passing moment is more real than the past and the future, but it is precisely passing and so, ultimately, unreal. The problem is not that our time is short, but that we are in time at all. The alternative, however, is present to us only as this blank sense of time's deficiency.
So, with unseeing eyes, we stand on tiptoes after all.