The present is really all that we have and it is all that we have to lose.
We can find ourselves stuck in past events, ruminating about what happened or what could have happened. Being stuck in the past, we lose the present and no matter how long we ruminate, nothing is changed.
We can speculate about the future, develop all sorts of plans and goals. But no matter how much we speculate, none of that becomes true and we lose the present moment.
In Tibet there is a story of a turtle that only visits the surface of the water every one hundred years. They ask a simple question, what are the chances that turtle comes up and happens to stick his head through a golden floating ring on the ocean's surface?
And that is how often we stick our heads up out of the surface of the ocean of thoughts, negative emotions, and the cacophony of daily life. Very rarely are we present, it is too easy to get swept away.
At the time of death, what we lose is our presence in the world. We don't lose the past or the future, those are beyond our reach. We lose our presence, the only thing we truly have and yet the thing that we so readily squander.
The call to action: come to the surface more often. Come multiple times a day. Don't wait for a hundred years until the time seems right. Be present, here and now.