It's easy to think of your retirement years as being all about you. After all, you've likely spent the last several decades devoting your time and energy to others — your boss, coworkers, clients, or kids. Now, you think, it's time to finally focus on yourself, and that's true to an extent. But your post-work life still needs structure and purpose. Without these two key pillars, life can get boring and lonely very quickly.

One very good way to fill the void is to give time and energy to others through volunteering. Sure, you won't walk away with a pay check, but the simple act of volunteering your time to a cause comes with numerous other very important benefits.

For retirees Ross and Carol Chenot, volunteering has made their golden years incredibly fulfilling. Ross volunteers with GleanSLO, an organization affiliated with the local food bank. "Because we live in a rich agricultural area, GleanSLO (San Luis Obispo is where the SLO comes from) volunteers go into the fields or orchards after the harvesters have gone through and they pick the leftover produce and donate to the food bank," Carol explains. "Literally tons and tons of food get donated that way."

Carol put together a series of neighborhood "learning sessions" — called Neighborly U — through which people can learn a new skill or hobby. The sessions range in topic, and include computers, crafts, cooking, volunteerism, travel, recreation, entertainment, and self-improvement. So far, Carol says she's conducted 75 classes and has had more than 650 people register. "It reinforces a value of generosity that we want to pass down to others," she says.

If you're not convinced about the benefits of volunteering, here are five reasons you should consider giving your time to others during retirement.

1. Volunteering helps you connected to the community

Working automatically gives you a sense of connection to the local people, businesses, and organizations. But so often, when retirees leave their jobs, this sense of belonging gets lost. Finding a way to volunteer and give back to the community helps recreate that sense of connection. Look for an organization or cause that you're passionate about and inquire about volunteering opportunities. Not only do you get to spend time doing something you love, but you also help create a thriving local ecosystem.

2. Volunteering gives you a sense of purpose

Leaving the world of work and suddenly finding yourself with nothing to do can be a harsh wake-up call to just how entangled your sense of purpose was with your career. Clinical gerontologist David J. Demko, PhD, says "sitting around with nothing to do, and all day to do it" can cause retirees to become inactive and, consequently, very dissatisfied and lonely. He adds that this mentality can reduce life expectancy by five to seven years. Volunteering can help you reinvent your post-work lifestyle with new roles that provide the structure and purpose you need.

3. Volunteering helps boost your mental health

Recent research found that seniors who give back experience a number of mental health benefits as a result: Anxiety levels and depression can be reduced in as little as one year spent volunteering. The National Institutes of Health also reports that seniors who participate in activities they enjoy — such as volunteering — may improve their cognitive functioning and reduce the risk of dementia as a result.

4. Volunteering keeps you physically active

Many volunteer positions involve physical activity, like walking or moving items, and there's no question that staying physically active is good for your health as you age. If you really want to make physical activity a focus of your volunteer experience, consider giving your time to a local YMCA, youth sports program, or school PE class. There's little downside to having something in your schedule that requires you to get up and get moving.

5. Volunteering helps bridge generational gaps

When retirees give their time to younger generations, both groups have a chance to learn from each other. Ross Chenot says volunteering with at-risk high school students in a continuing education classroom gives him a chance to connect with teens and helps the students work through their studies so they can graduate. "It's wonderfully rewarding to not only hear students hopes and dreams, but actually help them move toward realizing them," Ross says.

About 25 percent of Americans over the age of 55 say they spend some time volunteering, according to the U.S. Bureau of Labor and Statistics. That number has room to grow. After all, as Demko puts it, "everyone needs a reason to get up, get dressed, and out in the world, because meaningful lives are longer than most."