These four factors affect people's happiness at work.

What makes people happy at work? A recent survey from Robert Half and Happiness Works says fit, meaning, appreciation, and respect.

Overall, employees will be happiest if they're at a job and company that's the right fit for them. That influences pride in an organization—a big happiness driver. "When you hire people who mesh well with your workplace culture, they acclimate with greater ease and begin making substantive contributions quickly," reads the study.

Having meaningful work is a related factor; employees who say their work is worth doing are more than twice as likely to be happy than those who feel the job is "just work." According to the survey, professionals in the marketing and creative fields are the most interested in their work, and represent the happiest professions surveyed. In contrast, sales and customer service reps are the least interested in their work, and represent the least happy professions.

Feeling appreciated is another major factor. Study participants, regardless of country or gender, listed it as one of their top three drivers of happiness for them.

Similarly, being treated with fairness and respect is a key part of workplace happiness. Only 7 percent of U.S. workers say they "experience a high level of fairness and respect," and nearly a quarter of those who don't are likely to leave their jobs within the year. An important way people measure fairness is in compensation. For instance, the study found that technology professionals are most likely to say they are paid fairly. These individuals also report a fair work-life balance and, perhaps not coincidentally, they are the least-stressed profession surveyed.

So, what do the happiest people at work look like? They are senior executives aged 55 or older and in their first year on the job. And they work at a company with fewer than 10 employees; employees at these companies scored a 76 on a 100-point happiness scale, compared with a 71 average.