single-focused on any one thing....as in, while you are in it, focus all you have, but in case that is taken away from you, allow your mind to broaden so as to take in something new....
Freelancing has taught me that. You are immersed in a project, and the client suddenly decides to put the Finis sign...then what? chances are you feel your world slowly collapsing around you....well, this one project may have collapsed, but there are other things to life....may not be paying in terms of hard cash, but may be paying in other ways..idea is to let the mind freewheel - not an easy task, but great when it gets going.
It's like the mandala (nothing explains the impermanence of life better). A mandala is a Buddhist (and ancient Hindu) symbol which represents the Universe - a very broad definition...The thing is that a huge amount of energy goes into making the mandala......energy and time and effort and will.....and then, after it is made, it is wiped out......and the place is made ready for another to be made......