I believe everything has a limit. While personally i do multitask, but i only do this when i have so much to and very little time. But if I really want to put in my best, i usually focus on one thing at a time.
I do not think that multitasking is actually good. You have to manage many things at the same time and we are not actually designed to do that. A person should focus on specific thing in order to avoid mistakes.