A new University of Toronto Scarborough study shows that how mentally sharp you feel on a given day can make the difference between stalling out and powering through your goals. The findings suggest that sleep, pacing and mood may help turn more days into your best days.
Feeling mentally “on” might be worth nearly an extra hour of work a day, according to new research from the University of Toronto Scarborough.
In a 12-week study of university students, the researchers found that day-to-day swings in mental sharpness helped explain why people sometimes breeze through their to-do lists and other times struggle to get anything done. On sharper days, students set more ambitious goals and were more likely to complete them, from finishing assignments to tackling everyday tasks like cooking dinner.
Lead author Cendri Hutcherson, an associate professor of psychology at U of T Scarborough, noted the work was driven by a familiar experience.
“Some days everything just clicks, and on other days it feels like you’re pushing through fog,” she said in a news release. “What we wanted to understand was why that happens, and how much those mental ups and downs actually matter.”
Mental sharpness, as researchers use the term, refers to how clear, focused and efficient someone’s thinking is at a given moment. When people are sharp, concentrating, making decisions, setting goals and following through can feel almost effortless. When they are not, even simple tasks can feel like a slog.
Instead of comparing different people to each other, which is common in psychology, Hutcherson and her colleagues repeatedly tracked the same individuals over time. That allowed them to see how changes within a single person from one day to the next predicted whether they would succeed or struggle with their intentions.
All of the participants were university students. Each day, they completed brief cognitive tasks that measured the speed and accuracy of their thinking, and they reported on their goals, productivity, mood, sleep and workload. By pairing these daily brain-performance snapshots with real-life outcomes, the team could link mental sharpness directly to what people actually did, not just how they scored on a one-time test.
The pattern was clear: when students were sharper than usual, they not only checked off more of their planned tasks, they also tended to aim higher, especially on academic goals. On days when their thinking was less sharp, they were more likely to stall, even on routine responsibilities.
Those daily mental ups and downs mattered regardless of personality. Long-term traits such as conscientiousness, grit or self-control still predicted how well people did on average over the 12 weeks. But they did not shield anyone from having an “off” day.
“Everybody has good days and bad days,” Hutcherson added. “What we’re capturing is what separates those good days from the bad ones.”
One of the most striking findings was the attempt to put a practical number on what mental sharpness is worth. By measuring students’ cognitive performance over hours of work, the researchers could compare the impact of being sharper or duller than usual to simply working longer.
They found that a big boost in mental sharpness above a person’s own average was roughly equivalent to doing about 30 to 40 additional minutes of work that day. The flip side is that the gap between someone’s sharpest days and their dullest days could add up to about 80 minutes of effective work time.
In other words, how your brain is functioning on a given day can make the difference between a short, focused sprint and what feels like an extra class period’s worth of productivity.
The study, published in the journal Science Advances, also probed what shapes mental sharpness from day to day. The results suggest it is not a fixed trait but a dynamic state influenced by short-term factors.
Students tended to be sharper after nights when they slept better than usual, and earlier in the day, with mental performance gradually declining as the hours passed. Feeling motivated and less distracted was linked to higher sharpness, while more depressive moods went along with lower sharpness.
Workload told a more complicated story. Putting in longer hours on a single day was associated with higher mental sharpness, hinting that people can rise to meet short-term demands. But when heavy workloads stretched across an entire week, sharpness dropped, making it harder to get things done.
“That’s the trade-off,” added Hutcherson. “You can push hard for a day or two and be fine. But if you grind without breaks for too long, you pay a price later.”
Although the research focused on students, the implications reach far beyond campus. For anyone juggling school, work or caregiving, the findings highlight how everyday choices about sleep, pacing and emotional well-being can tilt the odds toward having more of those high-performing days.
Hutcherson noted the data point to some concrete steps people can try.
“From our data, there are three things you could do to try to maximize mental sharpness: getting enough sleep, avoiding burnout over long periods of time, and finding ways to reduce depressive traps,” she added.
That might mean protecting regular sleep schedules, building in recovery time after intense pushes, and seeking support or strategies to manage low mood and rumination. It could also mean planning demanding tasks for times of day when you tend to feel most alert, and saving more routine work for when your energy naturally dips.
At the same time, the researchers emphasize that no one can be mentally sharp every day, and that beating yourself up for an off day is unlikely to help.
“Sometimes it’s just not your day, and that’s okay. Maybe this is the day where you give yourself a little slack,” Hutcherson said.
Future research could explore whether similar patterns hold in different age groups and work settings, and whether interventions that improve sleep or mood can reliably boost day-to-day mental sharpness and follow-through. For now, the study offers a hopeful message: by paying attention to how we care for our minds and bodies, we may be able to turn more ordinary days into our most productive ones.