It's common to enter retirement with a prediction for your annual expenses, only to find you estimated low. Nearly two in five retirees spend more than they expected, according to a 2018 Global Atlantic Financial Group online survey. This can happen as you try out new activities, such as taking on new hobbies or traveling frequently. The uptick in free time might also lead to big-ticket ideas you hadn't foreseen, like a home renovation project or new landscaping.

If you want to reduce your overall spending, the first step is often a shift in mindset. When it comes to adjusting routines, "change can be intimidating but worthwhile," says Wade Rivest, owner of JDog Junk Removal & Hauling Westfield in Westfield, Massachusetts. "It's the beginning of a new and exciting path." Adopting a frugal lifestyle can help you stay on budget. Follow these strategies to painlessly downsize your lifestyle during retirement.

Don't be afraid to move. Even if you planned to stay in one location during retirement, you might find you're drawn to a different area. Perhaps there are grandchildren you want to see more often in another city. There might be a warmer climate that offers more activities to pursue throughout the year.

Before making any changes, look at the costs involved. "Downsizing in one area of life can mean upsizing in another," says Sara Zeff Geber, a certified retirement coach and founder of LifeEcore. Think about whether you could be just as satisfied in a smaller space with less to maintain that is close to family or allows you to pursue your favorite activities.

[Read: The 10 Best Places to Retire With Affordable Housing.]

Simplify your home. It's common to have boxes filled with your children's college memories and antique collections or kitchen appliances filling the basement or garage. "These areas of the home are natural havens for junk and items infrequently used," Rivest says. Reducing what you keep can bring you peace of mind and make it easier to clean. If it feels overwhelming, start with just one box or corner. Spread out what you have so you can see the belongings. "Go through these items and determine if anything can be resold or donated for reuse," Rivest says. You could bring in some income by selling what you no longer use. You might also find items you forgot about and can use in your home, thereby eliminating the need to make new purchases.

Travel mindfully. Perhaps you have a long list of places you want to see. Before booking trips, compare prices and seasons. It could be less costly to visit a spot during the low season. You might also decide to take just one annual big trip to spread out travel expenses from year to year.

You may have flown frequently for vacations during your working years to save time. With extra time on your hands, taking a car might be less expensive than a flight. Consider hitting the road to visit family and friends. Stop at free historical landmarks, museums or parks along the way.

Pay less for regular activities. If you shop at the same place or dine at a certain restaurant every week, check if you are getting the best price. "Before heading to the store or going out to lunch, do a quick Google search to see how much money you could save, or simply ask an employee," says Matt Dworetsky, president of Dworetsky Financial in Wall Township, New Jersey. In addition to senior discounts, you could enroll in a loyalty program. Theaters often offer a reduced rate for movies during afternoons or on certain weekdays.

[See: 8 Things That Matter More Than Money for a Happy Retirement.]

Get involved with what's close to your heart. Charities and nonprofit organizations are often looking for volunteers. Visit places that line up with your values or are related to the line of work you were in. If you spent decades in health care, you might find fulfillment donating several hours each week at a children's hospital. If you had leadership roles, ask about local boards looking to add new members. You could find satisfaction helping others, and you probably won't be spending money while you are volunteering.

Cut what you won't notice. Get rid of magazine subscriptions you don't read, TV channels you don't watch and landlines you no longer need. Then review your current plans and costs. You might be able to sign on for a less-expensive cellphone plan or television service. If you have two vehicles but generally only use one, ask if you need the second car. "With ride-sharing services available such as Uber and Lyft, perhaps it's best to only own one car," says Craig Kirsner, a retirement planner and author of "Retire With Confidence: Preserve and Protect Your Wealth and Leave a Legacy."