Miranda Kerr Calls Motherhood 'Most Incredibly Rewarding Experience' as She Reflects on Turning 40

Miranda Kerr is opening up about how being a mom has been one of the most fulfilling parts of her life.

Reflecting on her upcoming 40th birthday on April 20 and chatting about her launch from KORA Organics, the Plant Stem Cell Retinol Alternative Serum, Kerr talks about her life lessons in a video filmed by Alex Kenealy for KORA, shared exclusively with PEOPLE.

"Becoming a mother to my three beautiful healthy boys is really the most incredibly rewarding experience of my life," she says.

"I remember when I was pregnant with Flynn, I was quite nervous about bringing this little life into the world. And I feel like that's normal for a first-time mom to have those nerves — but with Hart and Miles, I've felt a lot more relaxed and empowered."

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The model, 39, shares sons Myles, 3, and Hart, 4, with husband Evan Spiegel, as well as son Flynn, 12, with ex Orlando Bloom.

On motherhood, she continues, "Being a mom has its challenges for sure, you know, not all days are so easy, but I really try my best to be patient and kind and nurturing."

"Being a mother has taught me that I'm so much more capable of more than I actually thought I was capable of. More love, more patience, more resilience. And I just learn so much from them every day."

While walking the red carpet of the 20th annual G'Day USA Arts Gala in Los Angeles in January, the model opened up to PEOPLE about her favorite part of being a mom.

"Just seeing the world through their eyes and the fact that they're all very different," she said. "They have different personalities, and they just bring something to the table that's just unique to them."

Noting that she has "very loving and very sweet boys," Kerr said, "I feel very grateful to have three kindhearted, good mannered boys."

"They're always like, 'I love you, Mommy. I love you.' And I'm like, 'Well, I love you more.' And then they start saying, 'I love you more,' and I'm like, 'Not possible,' " she continued. "Now they're saying to me, 'Not possible,' so it's funny how they mimic what you do, and actually, the thing about kids is they actually follow your actions."