Multitasking requires us to make decisions continually. Should I reply to a message now or later? How to answer it? How and where to save this message? Whether to continue the working process or take a break? All these minor decisions require the same amount of energy as important and significant, so they just tire a brain. We spend a lot of effort into small solutions, but there is a risk that we will not be able to make the right choice when it's necessary. We seem to understand what is important for us and what is not, but in the brain at the same place the same processes. We spend the same resources to make a decision pen of which color to take, and the decision whether to enter into a contract with a particular company or not.
Of course, there is no possibility to get away from multitasking at all. Nevertheless, there are effective ways to restore order in ones own mind, to become more productive and get more enjoyment out of life.