Jessica Simpson writes letter to herself on 42nd birthday: 'I know my purpose'

Jessica Simpson rang in her 42nd birthday with confidence.

On Monday, the singer shared an Instagram post of herself in a black cutout dress with a letter she wrote to herself in the caption saying it's "time to Rock 'n Roll."

"Oh lil Mrs 42 look at you leanin' into the moonbeams to recharge and radiate a purposeful glowing heart," she began. "I'm very proud of my faith, resilience and strength over the last 4 decades. Everything in my life that has or hasn't happened yet makes turning 42 very exciting because I know what it takes personally to remain inside of DETERMINED PATIENCE."

"I know myself and I do love her very much. I know my purpose and I must say that ladies and gents I am equipped to waltz within every dream I own confidently," Simpson added. "I am humbled and honored to finally be my own best friend."

In April, the mom of three shared how she built self-love over the years.

"I think loving all parts of yourself is a hard thing, but it also is the only way you can achieve it, it's to understand what that means, to understand what love is," Simpson told "GMA" at the time. "There is no way that you can love others as deeply as they deserve until you love yourself that deeply. And we deserve our own love first. And then from that love, it's very easily shared, and it's very believable."