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There may be no more highly anticipated event in a worker's career than retirement. Every year thousands will turn in their keys, clean out their desks and walk out of the office doors for the last time, leaving behind the world of work and entering the realm of golf courses, beaches and bird watching. This is a time to be celebrated and enjoyed.

But sometimes retirement is not all people anticipate. Here are five things you may not expect about retirement.

Loneliness

Many people make their best friends in the workplace, and rightfully so — 30 or more years of working shoulder-to-shoulder with others inevitably builds camaraderie. That friendship can be a huge part of a working person's life, and the loss of those daily interactions can leave a hole post-retirement. While many people might expect to spend more quality time with friends, they might find the opposite is the case and they end up feeling alone.

Boredom

Americans work a lot. In fact, over the course of a career, workers spend more time at work with their company and co-workers than at home. Much of our identity is shaped by our occupations, and no longer being active in that job can result in a feeling of purposelessness and boredom. While watching TV all day might sound appealing when you're always busy with demanding tasks, most find that within a short few weeks they are bored and feel mentally stale.

Running out of money

Retirement packages such as 401(k) plans and pensions are all important benefits to take into account when considering a job, and many people spend their careers carefully calculating how much money they need for a comfortable lifestyle in retirement. However, whether it's because of outliving their allocated funds or spending too much too fast, some find their resources are falling short. Fortunately, there are some options. Programs like reverse mortgages can be great additional resources of funds when the bank account is getting low.

Marital stress

While many dream of spending their remaining days with their beloved at the beach or in Paris, neither partner will be used to spending all day, every day, together after 30 or more years of being apart for at least eight hours per day. Both have their own routines and practices they've grown to like and expect, and having those upended can often cause added stress when both are home. Creating that new relationship can be challenging, but it also can be deeply rewarding when worked through together.

No increase in happiness

It's true in all stages of life: Many carry around the false idea of "I'll be happy when"... . Your newfound freedom may bring a rush of endorphins initially, but soon these retired days will become the new normal and your happiness level will return to where it was when you were working, or it might even dip below that. Take time to make the most of each day, find ways to feel purposeful and strive to strengthen those relationships most dear to you.