Why your brain can't let go of unfinished tasks, even something as minor as a half-written email

Sometimes when I’m not working, I find that I still am – in my head.

I could be at home, chilling on the sofa while watching an episode of the HBO series The White Lotus.

But somewhere in the background of my brain, some quiet thoughts are gnawing at me. I haven’t finished the legwork for my upcoming article. There are emails I need to reply to and ideas I should jot down lest I forget about them before the next team meeting. 

And it’s not just work. The undone chores around my home sometimes whisper, too. The laundry that hasn't been folded, the dishes still in the sink and the text messages from friends I meant to reply to yesterday morning. 

None of these tasks would be categorised as extremely urgent. Some aren’t even that important. But in those pockets of rest, they surface repeatedly, making it hard to disengage from my responsibilities and enjoy my leisure activity. 

It’s as if my brain doesn't fully trust the idea of doing nothing or getting a complete rest.

It seems that many of us carry the weight of unfinished tasks like invisible backpacks, even in our downtime. 

So why can't we let go of undone things, no matter how small they are? Why do work tasks cling to our minds long after we’ve logged off from our devices?

Curious about whether something like this has been explored in psychology, I did some research and found that psychologists have a name for this – the Zeigarnik effect. 

It is our brain’s tendency to keep reminding us about unfinished tasks more than those we’ve completed. That’s why some things stay “rent-free” in our mind, because they’re not done yet.

HOW DOES THE ZEIGARNIK EFFECT WORK? 

Elaborating on the Zeigarnik effect, the psychologists I approached said that the human brain is like a tab-hoarding browser, so the moment something is unfinished, it keeps that tab open and blinking until something is done about it. 

This was first observed by Russian psychologist Bluma Zeigarnik in the 1920s, after she noticed that waiters could remember complex orders only while they were in progress, but forgot them after the bills were paid.

Dr Geraldine Tan, director and principal psychologist from mental well-being centre The Therapy Room, said the effect itself is not a huge issue and it manifests even in everyday situations as a protective mechanism. 

“Let’s say you have a pot of water on the stove and you need to wait for it to boil before adding in the pasta. If you forget the water is boiling, it could be disastrous,” she said. 

“So sometimes, these thoughts linger because there’s an element of risk or consequence involved.” 

Even if it’s not dangerous, Dr Tan said the brain “parks” the thought and keeps it there until it is done, though some mental effort is required. 

"Like when you go to the supermarket and you hear someone saying, 'Oh I haven’t done this, I need to go home. I need to do this, I need to do that'. Oftentimes, this sounds like a complaint, but it’s just something the person is repeating to herself so she can complete her unfinished tasks."

However, with how fast-paced urban life is, these “parked” thoughts sometimes get pushed aside by other priorities.

Dr Tan explained that they do not disappear – they are just displaced, until something might trigger the memory again, forcing you to get back to the task eventually. 

Dr Ong Mian Li, founder and principal clinical psychologist from Lightfull Psychology and Consulting Practice, said one theory behind the Zeigarnik effect is that the human brain evolved from prehistoric times to prioritise potential threats or risks, also known as loss aversion. 

Back then, unfinished business could mean danger, such as forgetting where a predator was.

“So even today, your brain throws a mental tantrum when something’s unresolved, even if it’s just a half-written email ... it throws up a yellow or red light,” he added. 

HELPFUL FOR LEARNING, BUT IT CAN BE DRAINING  

This lingering mental itch nudging you to complete unfinished tasks has upsides in learning and working, since it functions like a built-in reminder system to help us finish what we started, the psychologists said.

Dr Tan said this is especially helpful in learning, such as how young children learning to tell time often get stuck on how the minute and hour hands relate, so the information feels incomplete. 

"That sense of 'I still don’t get this' drives you to revise, and that’s productive. If the task feels incomplete, the brain pushes you to go back to it and complete the learning."

In the workplace, the same effect can drive preparation, for instance, mentally rehearsing what to say in a meeting or revisiting a task list before work, Dr Tan said.

“It’s useful, but only as long as you act on it. If you don’t, the weight compounds. The effect lingers in the background, draining your energy.” 

Ms Eunice Lim, clinical psychologist from therapy outfit Heartscape Psychology, said that when this happens, it could contribute to fatigue, burnout, and negative self-beliefs around competence, especially in individuals with perfectionistic tendencies. 

People juggling multiple roles – work, caregiving, financial stress – often feel the Zeigarnik effect more intensely. Tasks start to bleed into rest time and even joyful moments can feel muted because the mind is still stuck in “unfinished” mode, Ms Lim added. 

“The mental strain of chronic incompletion can mimic hypervigilance, where the body stays on alert because it doesn’t feel safe to rest. 

“For some, this shows up as difficulty falling asleep, as their minds replay what they haven’t completed, what they should’ve done or what still hasn’t been started."

In some cases, it may even lead to depersonalisation, where one feels numb or emotionally disconnected as a way to cope, Ms Lim said.

Dr Tan said that this effect extends beyond short-term tasks because long-term unmet goals, such as a dream or a goal you haven't moved on from for years, can also be problematic when they loop in your head. 

"This can go in a few directions. You resign yourself to thinking, 'I’ll never do it', or you feel like you’ve failed, which can cause you to spiral downward.

"Or, you finally decide, 'Okay, when am I going to do this?' Then you make a plan, even if it's for later."

Dr Tan added that the bigger the goal, the more mental space it takes up.

COPING MECHANISMS AND HOW TO USE THEM TO YOUR ADVANTAGE

The good news is that there are simple tips and strategies you can adopt to mentally close the loop on tasks you are unable to finish right away. 

The psychologists suggested getting things out of your head and onto a list, which will help declutter the mind even if you’re not acting on them yet.

However, lists alone aren’t enough.

Dr Tan from The Therapy Room said that you also need to convert thoughts into behaviour, which means acting on at least one item on your list. 

“Start by reprioritising. Do the things you can do. Put a clear timeline to them. Once they’re done, they’re done,” she advised. 

“After that, you’ll realise that things aren’t so bad. And for the rest, you can throw them out if they are unnecessary, get help from others or just get started on another task.” 

Ms Lim from Heartscape Psychology recommended the “one-minute rule”. If a task takes under a minute to complete, do it immediately, because this helps close small loops and prevents build-up. 

She also said breaking big goals into small, actionable steps goes a long way, because a single goal can sometimes feel massive and overwhelming, thus leading to avoidance. 

For example, if you are unhappy with your career and have a goal of switching to doing something else, try listing three companies you are curious about from networking site LinkedIn or speak to a friend in that industry you are eyeing. 

Dr Ong from Lightfull Psychology said that the Zeigarnik effect can be used to our advantage. One simple way is to start a task and intentionally leave it midway before taking a break. 

“That little tension pull? It’ll motivate you to come back and finish it. Writers and creatives do this all the time,” he added, explaining that this was the same psychological trick behind the cliffhangers of shows you watch.

Another mind hack: just tell yourself you’re going to begin a task to nudge yourself into action gently.

"Chances are, your brain won’t let you rest until you come back to it. This is really helpful for procrastinators," Dr Ong added. 

He noted that the Zeigarnik effect is more pronounced today than it was 10 to 15 years ago. Back then, most people had just one email inbox to manage.

Now, “we have six inboxes, three messaging apps and a smartwatch reminding you that you’ve only done 5,000 steps.

"It's not just about how many inboxes we have, it's the sense that we’re never quite done. There’s always one more notification, one more ping, one more thing we could be optimising.

"The modern challenge isn’t just about finishing things. It’s about deciding what’s worth finishing. And sometimes, the healthiest thing you can do is close a mental tab with a shrug and say, ‘Not today, and that’s okay’."