Doing Many Things And Completing Zip

I don't know how effective "multi-tasking" is when it wears a person out in the end. Seems like the only accomplishment that has been made is the depletion of energy of the body and soul. Should we prove that we're capable of doing so many things at once or is it better to show we can do many things, just not at the same time? I would like to say that I work my best doing one thing at a time very well and if I want to and able, will add on more. Success feels more rewarding to me when I know what I can handle and knowing when I can do more. Depending on how I'm feeling for the day I may just want to focus on one thing instead of a dozen others. We seem to cram so much in at once and we wonder why we resent what initially gave us pleasure in the first place. Just saying, what are we rushing for to complete by many deadlines at a time?!? Americans we are overworked. Adapting a new way of managing work could do us good.