Zachary has been trying to work on an essay for almost three hours, but he can't seem to focus for more than 15 or 20 minutes at a time. what should he do so that the quality of his work doesn't suffer because of poor concentration and lack of energy?

There are many reasons why Zachary can't concentrate. He might have something on his mind that is bothering him, he could be hungry, he could not have a lot of energy. The best thing Zachary could do to help the paper not suffer is leave his desk and paper alone for about a half an hour, and maybe eat something, or just take a break. Maybe take a nap to get some energy back up so that he can get everything he needs in his paper. 

The best way is to swollow and hold in your breath