Michelle Obama Pays Tribute to Late Mom Marian on What Would’ve Been Her 87th Birthday: 'She's Worth Celebrating'

Michelle Obama is paying tribute to her late mother Marian Robinson on what would have been her 87th birthday.

On Monday, July 29, the former first lady wrote on Instagram that even though her mother is "no longer with us," Robinson is "worth celebrating."

"Today would have been my mom’s 87th birthday. These past couple of months have been tough without her, and I am so grateful for the outpouring of love you’ve shown our family along the way," the Becoming author began her post. "Even though she’s no longer with us, I still think she’s worth celebrating."

Obama, 60, then shared what she loved most about her mother, who died on May 31.

"She always felt like she was enough. The tiny two bedroom walk-up apartment we used to live in; the faux chimney she would fashion for us out of cardboard during the holidays; the at-home hair-dos she would give herself using the oven and a hot comb — she was always happy with what she had."

Obama continued: "And because she felt like she was enough, she could help others feel that too. She did that countless times for me and my brother Craig. She did it for her family and friends. She did it for the staff at the White House. She did it for everyone she knew."

The former first lady wrote that for Robinson's birthday, she is celebrating "the immense power there was in her enoughness."

"And I am committing myself to carrying forward her legacy of lifting up others the best I can," she added.

Obama concluded the post with: "Love you, mom. And happy birthday."

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.

Robinson was a staple at the White House during her son-in-law Barack Obama's presidential administration. She stayed with the first family, who called her "grandma-in-chief," at 1600 Pennsylvania Avenue, moving from her lifelong home of Chicago.

"We needed her. The girls needed her. And she ended up being our rock through it all," the family said about Robinson's presence at the White House in a statement announcing her death earlier this year.

"She relished her role as a grandmother. ... And although she enforced whatever household rules we’d set for bedtime, watching TV, or eating candy, she made clear that she sided with her 'grandbabies' in thinking that their parents were too darn strict."

The statement concluded: "In our sadness, we are lifted up by the extraordinary gift of her life. And we will spend the rest of ours trying to live up to her example."

Obama's father, Fraser Robinson, died in 1991.