Setting goals for yourself is key, but don't be too hard on yourself in the process, warns Piskin. Over-exercising and pushing yourself too hard when you first get started is one way to set yourself up for burnout or even injury.

"The name of the game is longevity. While your 2019 resolution might have been to get healthy and strong it really isn't only about 2019 — it is about creating a healthy lifestyle and infusing healthy fitness habits into your existing life for the long term," Piskin says.

Yang concurs, adding that it's too easy to feel like you've failed — which leads to quitting altogether — when your goals are too lofty.

"Have you ever set a goal of going to the gym three times a week, only to have a week of work travel come up that forces you to skip a whole week of workouts? Have you ever then returned and said, 'Screw it. I failed' and then find yourself not going back to the gym?" she says. "Goal-setting and creating structure are important, but it is critical to realize that having a perfectionist attitude will keep you from achieving your long-term goals."

Be flexible, be realistic, and be ready to forgive yourself. Trust that a normal life means ebb and flow and that this is all about long-term success.

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