We often feel the urge to 'take a break' after an hour of studying or work, but a new study has revealed that it's all in your head.
The Stanford researchers' findings challenge the long-held theory that willpower is a limited resource that needs to be replenished.
Usually, scientists argue that when willpower is drained, the only way to restore it is by recharging our bodies with rest, food or some other physical distraction that takes you away from whatever is burning you out.
But the new study says otherwise.
"If you think of willpower as something that's biologically limited, you're more likely to be tired when you perform a difficult task," said Veronika Job.
"But if you think of willpower as something that is not easily depleted, you can go on and on," she added.
Job conducted the research along with Stanford psychology Professor Carol Dweck and Assistant Professor Greg Walton.
In the study, the scientists found that after a tiring task, those who believed or were led to believe that willpower is a limited resource performed worse on standard concentration tests than those who thought of willpower as something they had more control over.
Students who bought into the limited resource theory also ate junk food 24 percent more often than those who believed they had more control in resisting temptation.
"Willpower isn't driven by a biologically based process as much as we used to think. The belief in it is what influences your behaviour," said Walton.
The paper is published this week in Psychological Science.