Are you already counting down the hours until 5 p.m.? Better refocus your thoughts. A new study from Penn State University finds that just believing your day will be stressful can cause you to be less productive.

Having negative thoughts about upcoming meetings and events in your day causes your working memory to weaken, which controls your ability to concentrate, on top of processing and retaining information.

According to Jinshil Hyun, a doctoral student in human development and family studies: ”Humans can think about and anticipate things before they happen, which can help us prepare for and even prevent certain events. 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.”

For the study, researchers asked a group of 240 adults to answer questions regarding their stress level seven times a day via smartphone app. The app polled them on their stress level each morning, and five times throughout the day. Before bed, they were asked how stressful they anticipated the next day to be. They were also tasked with measuring their working memory five times during the day.

Results showed that participants who worried about their forthcoming day in the morning performed worse on the working memory quizzes later. Researchers noted that even if participants’ stress levels went down throughout the day, their premeditated negative thoughts affected their cognitive function.

In the study’s press release, Martin Sliwinski, director of Penn State’s Center for Healthy Aging said: “When you wake up in the morning, you have a certain outlook for the day, in some sense the die is already cast. If you think your day is going to be stressful, you’re going to feel those effects, even if nothing 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.”

Sliwinksi notes that this could be much more difficult for those who have important deadlines, meetings or projects and need their productivity to be at a high. He goes on to emphasize that waking up with a more optimistic outlook on the day can make all the difference. And interventions might be as close as your smartphone’s “reminder” function.

“If you wake up and feel like the day is going to be stressful, maybe your phone can remind you to do some deep breathing relaxation before you start your day,” he suggests.