Anne Kadet, WSJ:

If you're wondering why it's hard to juggle new roles, ask a neuroscientist. Recent research suggests that multitasking can reduce productivity, because it takes a ton of mental energy to switch from one task to the next. The sheer number of hours demanded by the superjob also can impair your performance as your brain gets fatigued...</p>

You might want to put some of those hats in a closet.