The singer and actress, 41, shared a photo of herself on a treadmill in her home gym and said she had been putting off exercising.
"First day back at it and I'm already hurtin' and feelin' real dramatic about being sore," she wrote on Instagram. "I have been craving this, but procrastinating."
With the first one under her belt, Simpson said she's going to make it part of her day again — with a treat as an incentive.
jessica simpson/ instagram Jessica Simpson
The author of Open Book has been candid about her struggles with body image and weight loss throughout her career, and said in April that she threw out her scale. Now, instead of worrying about the number of pounds she weighs, Simpson instead focuses on how she feels.
"I have no idea how much I weigh, I just want to be able to feel good and zip my pants up. If I don't, I have another size. I have every size," she said on Today.
"I've really tried my hardest to not let that define me," she added, referring to when she would track her weight on a scale.
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Simpson, who dealt with plenty of scrutiny about her weight during her daisy dukes days, told PEOPLE in March that she's worked to move on from those days of body shaming, which she had recounted in her bestselling memoir.
"There is a wonderful movement for body positivity now and the response to that portion of my story has been overwhelmingly supportive," she said. "I don't think people always realized that there was a human being, a beating heart and working eyes with actual feelings behind those headlines and that words can hurt and stay with you for a lifetime."
Simpson said that she "spent so many years beating myself up for an unrealistic body standard that made me feel like a failure all of the time. I am still a work in progress when it comes to self-criticism but now I have the tools to quiet those voices in my head when they speak up."