Nobody likes getting up on the wrong side of bed, but it turns out the way you feel in the morning is much more than just an emotional haze.

New research reveals that people who wake up expecting to have a stressful day can actually impact their own cognitive functioning throughout the day – with the simple act of anticipating future stress putting a measurable bottleneck on our brainpower.

In a sense, the only thing to fear seems to be fear itself – because the researchers say even if the stressful experiences you're dreading never occur, just by internally forecasting them you're diverting precious, limited resources from your powers of memory.

"Humans can think about and anticipate things before they happen, which can help us prepare for and even prevent certain events," explains one of the researchers, cognitive psychologist Jinshil Hyun from Pennsylvania State University.

"But this study suggests that this ability can also be harmful to your daily memory function, independent of whether the stressful events actually happen or not."

To test their hypothesis, Hyun's team recruited 240 people aged between 25 to 65 years old to take part in a two-week experiment. Every day, the participants would be pinged by a smartphone app, asking them about their stress levels.

In the morning, the prompt would enquire whether they expected their day ahead to be a stressful one. Then, five times throughout the day, they'd have to rate their current stress levels. Finally, at night, they'd respond on whether they thought the following day would be stressful.

In addition to gauging their current or anticipated stress, each member of the group also had to complete a number of working memory tests during the day, in which they were challenged to remember arrangements of dots on a grid.

At the end of the experiment, the researchers found that higher levels of stress anticipation in the morning were associated with poorer working memory later in the day – although, interestingly, stress anticipated in the evening was not a predictor of worse working memory performance the next day.

But as for waking up on the wrong side of bed, the results were significant, which the researchers ascribe to what they call 'attention depletion' – with stressful thoughts sapping our attentional resources and impairing attention-demanding cognitive performance.

"Importantly, the effect of stress anticipation was over and above the effect of stressful events reported to have occurred," the researchers write, "indicating that anticipatory processes can produce effects on functioning independent of the presence of an external stressor."

Just like how people often say breakfast is the most important meal of the day, the findings suggest your morning's emotional perspective is an important, self-perpetuating foundation for what the rest of your day could look like.

"When you wake up in the morning with a certain outlook for the day, in some sense the die is already cast," says one of the team, neuropsychologist Martin Sliwinski.

"If you think your day is going to be stressful, you're going to feel those effects even if nothing stressful ends up happening. That hadn't really been shown in the research until now, and it shows the impact of how we think about the world."

The researchers say they now want to investigate using their findings to develop psychologically based stress-reduction interventions – but in the meantime, it's a healthy reminder to embrace positive thinking when the Sun comes up.

Today is going to be amazing. Today is going to be brilliant. Today is going to be out of sight.

The findings are reported in The Journals of Gerontology: Series B.