|It's now. Do you know where your attention is?|
There's nothing more important than giving the present your full attention. Do what you do fully and completely.
You can get to this principle from lots of different angles; there may be something to it.
Focusing completely on what you're doing is part of getting into 'Flow' which is associated with satisfaction.
On the ISS, Astronauts are trained so thoroughly that they can focus completely on what they're doing at that moment, and execute it flawlessly. ISS Commander Chris Hadfield learned about this level of focus flying jets: "If it doesn't matter for the next 30 seconds, then it doesn't exist".
This matters when you're driving too. It's far more dangerous than most other things you do in a day. If you can't focus on the safe guidance of of the ton or so of metal you're sitting in, you put yourself at risk.
Eckhart Tolle wrote a book called "The Power of Now" which approaches this level of focus and engagement with what you're doing from a spiritual angle.
Multitasking has been shown to be less productive than single tasking. You might feel more productive, but you're probably not.
David Allen (the Getting Things Done guy) recommends trusting a system for your next actions. Then you can be comfortable with what you're not doing and focus completely on what you're doing.
If you pay attention to what you're doing you'll do it better and get more satisfaction out of it.