Everyone has good and bad days at work, but when an employee has too many bad days, he or she may start strategizing to leave that job behind. If you've worked hard to get the best possible people on your staff – the ones most desirable to your competitors, needless to say – you don't want to lose them due to situations you could prevent.

Here are eight top reasons why employees quit their jobs. Take a hard look at whether your company is risking the loss of key staffers.

Washington Post contributor Libby Hoppe knew on the second day of a new job that she would quit – and she did, just two months later. What drove Hoppe to resign were the rigid timekeeping rules in her office, which didn't allow her the flexibility to handle her family responsibilities. When she had to pop out of her office to take care of a sick child, she found she was penalized by losing vacation time. Family or other responsibilities can require flexibility that an employer is unable or unwilling to provide. In those cases, employees sometimes find it easier to quit than to rearrange their family obligations.

Good employees are often capable of doing more than they are initially tasked with, which can be a tricky problem. That level of capability can result in an employee being asked to do more work than he or she can handle, which can lead to long hours, frustration at contributing more than the rest of the team and, ultimately, burnout. Alternatively, capable workers may complete their tasks and hit roadblocks when they request more work; the resulting boredom and lack of fulfillment on the job can be just as toxic as being overworked.

Many employees leave jobs when there is no upward mobility. No matter how hard they work or how well they succeed, there are no opportunities for advancement into higher-paying, more demanding positions. Alternatively, if a less qualified or less capable member of the team gets a promotion, high-performing employees may look elsewhere – especially if a former teammate becomes a manager.

Unfortunately, in many companies being a manager is considered a step on a typical career ladder, regardless of an employee's skills. Managers require expert communication and interpersonal skills, yet not all managers have these skills or are given the training to gain them. Too many managers have never been well coached themselves, says Leigh Branham, founder of the consulting firm Keeping the People, Inc. Lacking a good role model, they either give no feedback and coaching at all or [they] revert to the ‘YST' model – yelling, screaming and threatening. Most managers fear giving honest feedback, mainly because they haven't been trained to do it well.

Unclear communication of expectations from a manager can leave both employee and employer frustrated and unhappy in the work environment.

While the ideal workplace would include professionals behaving professionally, not all personalities mesh so easily. Interpersonal conflicts, office gossip, recognition-grabbing or undercutting of coworkers can lead to a toxic work environment, which might make a capable employee consider quitting. An additional problem may be interoffice competition: Even when flexible hours and vacation time are generous, a competitive workplace might prevent employees from feeling like they can use their benefits or flexible work options without getting penalized. Having difficulty scheduling vacations, or being discouraged from doing so, can also lead to employee dissatisfaction. Research has shown that taking full advantage of vacation time actually improves production, so encouraging a workplace culture where people can unplug and relax will benefit everyone. (See What Makes a Great Workplace? for specifics on what attracts employees.)

Raises are miserly, recognition is rare – neither of these company attributes is going to foster company loyalty among employees or encourage them to put in extra hours over the weekend. When employees do good work, they should be recognized financially and publicly. Otherwise, someone else will!

A generous benefits package can often be as much of a lure to employees as a generous salary. Funding for professional development or education, good health insurance, generous sick days, flexible hours, telecommuting options, more-than-the-minimum paid maternity and paternity leave, ample vacation time – these are the kinds of benefits that can help a company retain workers or, when they are not provided, drive an employee to look for a better package elsewhere.

Benefits don't even have to be large to be appreciated – something as seemingly minor as snacks at meetings can make a big difference (no meeting without eating will keep blood sugar steady and employees happy). Planned social events can also go far to gain employee loyalty and forestall a toxic work environment.

Switching jobs multiple times over the course of a lifetime has become the norm: Most people born in the late baby boom (1957-1964) have had 11.7 different jobs between the ages of 18 and 48. If one career field is not fulfilling, it is now fairly common for workers of all ages to start new careers unrelated to the path they originally embarked on. (If you are considering retiring because of lack of job satisfaction, see Don't Retire Early – Change Jobs Instead.) Talking with employees about ways in which they can stay in their job while continuing to learn and grow may help companies retain high-performing individuals.

As billionaire financier Sir James Goldsmith famously said, If you pay peanuts, you get monkeys. While there are many reasons why an employee might quit, rewarding good work with appropriate pay, benefits and recognition creates an environment that lets employees know they are valued. The best way to retain your employees? Ask them what they want and work with them to make sure everyone gets what they need. For more, see Top 5 Ways to Retain Your Best Employees.