We cannot always live feeling "in the moment" or just do one task at one time with our total being. There is a time for feeling in the moment, but we need not feel "in the moment" every moment (
Some people believe that the point of Zen Practice is to learn to "always be in the moment", every moment ... just absorbed in one task, not thinking future or past or any other thing.
However, I do not know anybody ... Zen folks included ... who can or should be like that all the time.
I think that is not true, nor very realistic. It could even be deadly, if one were "so in the moment" that one did not recognize that the road ahead leads right over a cliff!
I believe that such "being in the moment" is a skill we develop in the Practice, one of many skills, that we can "pull out of the tool kit" when appropriate, and put back when not. We do not live like that every moment, and only should in the right moments. When drinking tea, just drink tea ... but then the coffee break is over, the boss is yelling, the clients demanding ... and 10,000 other things to do!
There are other times in life when it is perfectly appropriate to be lost in thoughts recalling the past, or planning for the future. There are times when we can be completely distracted and even overwhelmed. At those times "being in the moment" means being fully at one with however life is in that moment ... if it is momentarily chaotic, be "at one" with that.
When doing one thing ... drinking tea, working in the garden, sitting Zazen ... just do that one thing. Yes, that is true. But a moment of "multi-tasking" is also "one thing" too ... called "multi-tasking". So, when multi-tasking, just multi-task ... just do that one thing whole heartedly in that moment too.
Folks encounter lots of Zen teachings like "when you eat, just eat. When you sleep just sleep..." But those Zenny words can sound rather idealistic if they imply that we must be "mindful" or in "Zen Mind" 24/7. (Don't misunderstand me, I think it a good power ... and it is just the "24/7" I am protesting). My view is more balanced I believe, namely, that "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. (If one ever visits a large Zen monastery, you might be surprised at how hectic things can get ... guests visiting, phones to answer, ceremonies to arrange, robes to clean, bills to pay and food orders to make ... it is quite like any business office in the administrative office of the monastery).
However, one of the great fruits of our Zen Practice is that, even when we are distracted, overwrought and multi-tasking, feeling completely rushed 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 even on cloudy days]. So I say, when feeling completely "rushed and off balance", just be "rushed and off balance" in that moment ... it too is a temporary state of mind.
If you try to be "Zen" 24/7 you are trying to be a "Zen robot" ... not a true human being who, for better or worse, will often be in human situations reacting in a human way. We do get better and better, through this practice, at finding our center and stillness amid the storm ... but so long as we are living as humans, we will always be human.
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.
Some moments, be "mindful" and "in the moment" ... other moments just be "at one with the moment" even if a moment when you are not "in the moment" that moment ... In other words, JUST DO THAT! IT TOO IS A PERFECT ACT IN THAT MOMENT!! :D