A growing body of research has begun to focus on a particular mental limitation having to do with your ability to use a mental trait known as executive function — thought processes require conscious effort to focus or make decisions.

But executive function draws upon a single resource of limited capacity in the brain. When this resource is exhausted, your mental capacity may be severely hindered. Even unrelated activities that tax the executive function have important lingering effects, and may disrupt your ability to make such an important decision.

These findings have important real world implications. If making choices depletes executive resources, then later decisions might be affected adversely when you are forced to choose with a fatigued brain. Basically, your brain is like a muscle — when it is depleted, it becomes less effective.