I liked to think I am productive, and most of the time I try to cram and do as many things as I can.  It is like a personal victory to be able to juggle as many balls as possible without letting any fall. 

On retrospect, that is fine for menial tasks.  If I am able to do 5 menial tasks at a time, then those menial tasks must not need much concentration and brainpower to do.  If that is so, maybe one of our employees, or assistants should be doing it.  Would I say I am maximizing my worth by doing easy tasks 20 or 50% faster than my people? 

Or should I be focused on doing the things that my people cannot do, and if they can do it ( even albeit slower or slightly less good than I could do?), they should.

Anything worthwhile doing is worth doing well, and is well worth done well by concentration, not while juggling 3 balls in the air.  After all, what will move your plans forward is not the many small tasks you can do, but the few challenging tasks you focus on — something that needs concentration and think time.