A good mood in the working places not only promotes a productive output from the workforce but a lasting working relationship among professionals.
Among the x-factors that most people look for in a company is how they can blend well with the other people who are under the payroll of the company. Most people, despite taking home fat salaries and benefits cannot really last in an organization where there is a tense mood and ambiance, sometimes contributing to personal factors such as having to drag their feet going to work, just to be able to earn a living.
While people often look forward to seeing the usual faces daily where they can be able to perform their assigned duties, nothing beat the idea of enjoying the company of their co-employees each time they report for work.
A good article on this can be elaborated here: Employee Motivation, Recognition, Rewards, Retention.