Focus is important in life, but not at the expense of everything else, if we miss one thing that happens we may as well miss everything that happens, just as every moment is a whole moment not a part of a whole moment.
Life should be a whole experience, but what is a whole life? I think it is a life not bound by past, or future, not caught up in doing everything at once, not looking at the big picture and missing the tiny details.
If we let go of what was, and what could be, then focus on the now we become unprepared for the future, but if we let go of worrying about the future and focus on what is, what we are doing we will never need to regret what has been and we will be prepared for the future.
As Ajahn Chah once said if we let go a little there is a little peace, if we let go completely there is complete peace.
At the end of the day I may be right, I may be wrong, but I share this hoping I am one or the other.