In life, there is only the present moment, the now. You can't measure time the way you measure the distance between two points. 'Time' doesn't pass. We have enormous difficulty in focusing on the present; we're always thinking about what we did, about how we could have done it better, about the consequences of our actions, and about why we didn't act as we should have. Or else we think about the future, about what we're going to do tomorrow, what precautions we should take, what dangers await us around the next corner, how to avoid what we don't want and how to get what we have always dreamed of.
It's being here now that's important. There's no past, and there's no future. Time is a very misleading thing. All there is ever is the now. We can gain experience from the past, but we can't relive it, and we can hope for the future, but we don't know if there is one.
The biggest mistake we make is the one that most of us make; we do not live in the moment enough.