Pretending to be happy can actually make you more miserable - especially if you're a woman, according to a new study.
Researchers found that walking around with a forced smile and faking happiness simply led to people feeling gloomier.
So, putting a brave face on your woes could actually be counterproductive.
The research found that women suffered more than men when pretending to be happy.
Psychologist Dr Brent Scott, who led the study, said employers should take note because forcing workers to smile when dealing with the public can backfire.
He said: "Smiling for the sake of smiling can lead to emotional exhaustion and withdrawal, and that's bad for the organisation."
Dr Scott said the research showed customer-service workers who 'fake smile' throughout the day worsen their mood and then withdraw from work, so their productivity drops.
He added: "Bosses may think that getting their staff to smile is good for the organisation, but that's not necessarily the case."
Dr Scott, assistant professor of management at Michigan State University, analysed a group of bus drivers during a two-week period.
The study is one of the first of its kind to examine emotional displays over a period of time and compare the different effect that has on men and women.
His team examined the effects of surface acting - or fake smiling - compared to what was termed 'deep acting', or cultivating positive emotions by recalling pleasant memories.
Dr Scott said: "Women were harmed more by surface acting, meaning their mood worsened even more than the men and they withdrew more from work.
"However, they were helped more by deep acting, which means their mood improved more and they withdrew less."
Dr Scott suggested women tend to suffer more when pretending to be happy because they are expected to be more emotionally expressive than men.
Therefore, faking a smile while feeling down is more likely to go against their normal behaviour and cause more harmful feelings.
Although, 'deep acting' seemed to improve mood in the short-term, Dr Scott says it's not a long-term solution to feeling unhappy.
He said: "You're trying to cultivate positive emotions, but at the end of the day you may not feel like yourself anymore."