It seems there is one in every office - the employee who is always the first to arrive and last to leave.
While bosses may view it as a sign of dedication to the job, it could instead be a symptom of a major problem: stress.
"You may think to yourself that's great because they're staying so late. But actually I would say to you, 'why are you staying so late?'" says Carole Spiers, a stress consultant.
"Is it because they have so much work to do? Is it that they don't understand what they should be doing? Is it that they have really not got a feel for the tool, and no one has shown them what to do? Or is it because no one has shown them how to delegate? There are all sorts of reasons."
Many people mistakenly believe stress helps them to get things done. But Ms Spiers says they are wrong. Pressure is the motivator, and stress is simply excess pressure.
People experiencing stress at work are more likely to have sleepless nights, headaches and find it difficult to manage their time. Their performance, morale and, ultimately, the company's profitability, will suffer.
Management has a big role to play by identifying and helping employees who are showing the symptoms of stress.
"They need to be aware of those in their team, so reading the warning signs: employees who are not working well, they're not productive, or you've got an employee who may be staying till 8 or 9 or 10pm at night," says Ms Spiers, who has just published a book called Show Stress Who's Boss, which includes tips and strategies to help sufferers to cope.
But what does a boss do if he or she notices that an employee is suffering from stress? Talking to the employee is a good start, says Ms Spiers.
Managers may complain that they do not have time, but they cannot afford to ignore the problem.
"Ultimately it is going to cost you time thereafter, because that employee is going to take time off work, and then it's going to cost you more time to get that employee back," she says.
Employees can also help themselves by taking control.
"We're becoming a slave to our emails, a slave to our BlackBerrys and iPhones, and it should be the other way around. It's meant to be helping me, not hindering me," she says.
If an employee has to break away from a piece of work to deal with emails, they should simply switch them off.
You will have to deal with them eventually, but it is far easier doing it in chunks of time. If you receive 100 emails a day, Ms Spiers suggests tackling them in four allotted slots.
"You have to think of a body as a machine. Our car is also a machine. If you get a red light flashing on the dashboard, the chances are you are going to go into the garage in order to get it fixed," she says. "If we see a red light flashing on our own dashboard, the chances are we're going to ignore it.
"We think we can beat the system, but you can't always beat the system. So take control, know what to do and take action."
