The Dancing with the Stars pro, 27, who welcomed her first baby, daughter Sage Jill with husband Samuel Lightner Cusick in November, commemorated the special occasion on Sunday with a sweet post on Instagram.
"Sagey girl 💕 Being your mama is the greatest blessing of my life. I love you with my whole entire heart which seems like it has grown 10 times bigger since you came into our lives 😭," the mom of one wrote, along with portraits of her and Sage as well as one from her pregnancy.
"I am eternally grateful for you and grateful that you chose me. I promise to give you all of my love and support for the rest of forever 💕💕 #mothersday #mom #mamasgirl," Arnold added.
The star also gave a shout-out to the women in her family. "Happy Mother's Day to my beautiful and perfect momma @mindy_arnold 💕💕 I could not be more grateful for you and the love you give to all of us girls every single day. You have been the best example to me of how to love and support your children in all they do! I love you so much 💕💕 #mothersday #mom #grateful," Arnold shared in a separate Instagram post.
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Last month, the new mom shared a post on Instagram about how fast her little girl is growing up. "It's in these moments where I actually wish time could just stand still 😭 ," she began the loving post. "Sage will be 6 months old in 4 days and I'm sitting here wondering how time has literally flown by faster than it ever has."
"I'm assuming that's what life with kids is like right? Time going way too fast and our babies growing up way too quickly 😭," Arnold continued.
The dance pro went on to explain why it feels so bittersweet to watch her daughter get older.
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"I love watching her grow and change and learn new skills but i also want my baby to fall asleep on my chest for the rest of forever 😂," she concluded the post.
Earlier this month, Arnold spoke to PEOPLE about the pressures of being a mom and how she reminds herself that no parent is perfect.
"I try to focus on the fact that there must be so many moms out there that are feeling these same pressures," she said. "And if I can be open and vulnerable about it, maybe I can help other moms who are feeling the same way, and understand that it's okay and that none of us are perfect. There are trials when you're a mother."
Arnold continued, "There's things that you're still learning and trying to grow every single day and you're not alone. That's kind of what drives me. And at the end of the day, I try to focus and remember that I know what's best for me and my family."