I sometimes describe the many perspectives and states of mind that we can master through Zen Practice as "tools (or non-tools) on the toolbelt". We may take them and be them at the appropriate moments, then replace them on the belt.
So, sometimes we can be fully in the moment, no thought of past or future, no thought of other places to be or where we would better be. Such moments might include watching a sunrise, playing with our children, enjoying and experiencing just this one place and time of life. It may be pouring oneself into Zazen, Oryoki, Samu, Calligraphy, Archery, the Tea Ceremony.
Other times, we might need to think of the project we have to do tomorrow, the place we have to go next, the many things we have to do on the "to do" list.
Or, other times, we might think of something that happened this morning or many years ago, good or bad. It might be the sunrise we saw yesterday, or the fight with the wife 5 minutes ago, or what the boss said last year.
Without the future or past, we could not live as human beings. I am reminded of the story of the man with the brain injury who had no past, no future ... and thus could not function in the simplest tasks.
I believe, though, that even when we are in those "present moments" when we are thinking of the "must do's" and "what if's" of the future ... hold them lightly, be willing to let be what will be (even as you work you plans to turn the future your way). Even when in those "present moments" when we are thinking of the past ... hold memories lightly, be willing to let what was, just be what was (even as we learn from the past).
So, yes, when driving the car ... probably a good idea not to be so caught up in the fight with the wife that morning that you fail to notice the semi-truck in front of you! :shock:
I think that there are times to be mindful in our practice in that way, and great lessons are to be learned there ... drinking a cup of tea as the only and perfect act in the whole universe of that moment, the same for "Oryoki" meals during a Sesshin, "just being" in the moment, when washing the floor "just washing the floor".
But the one point I really really really wish to emphasize to folks is not to be too idealistic about what "mindfulness" is, or set it up as some unrealistic goal. I described it recently when I said this ...
[Folks encounter lots of Zen teachings like the one mentioned by Master Seung Sahn, "when you eat, just eat. When you sleep just sleep..."] But I think that Master Seung Sahn's phrasing, like many Zen books and expressions, can sound rather idealistic if it implies that we must be "mindful" or in "Zen Mind" 24/7. My view is more balanced I think, namely, "when mindful of one thing, just be mindful of one thing ... when distracted, overwrought and multi-tasking, just be distracted, overwrought and multi-task". There is a time for everything, and we cannot be "mindful" each minute. All of it is life.
However, one of the great fruits of our Zen Practice is that, even when we are distracted, overwrought and multi-tasking, feeling completely miserable and off balance ... and even when "Zen Mind" feels very far away ... we can still know it is 'there' even if we do not feel it at that moment, the blue sky always behind the clouds. So I say, when feeling completely "miserable and off balance", just be "miserable and off balance" in that moment ... it too is a temporary state of mind.
So, in other words, have a balanced and realistic view of life ... even a balanced view of sometimes or frequently being unbalanced, overworked, distracted and such.
It seems to me that many people in Zen Practice have come to confuse "being present/mindful in the moment" (for example, "when drinking tea, just drink tea" ... a sometimes appropriate and lovely way to experience life) ... with "being at one with the moment" (allowing and merging with conditions of life "just as they are"). The two are not quite the same, and are often confused, and the latter is much more at the heart of this Shikantaza Path ...