Inside Britney Spears' 40th Birthday Bash in Mexico as She "Finally" Feels Like Her "True Self"

Britney Spears is doing somethin' big for her birthday.

A source tells E! News that the singer—who turned 40 on Tuesday, Dec. 2—and her fiancé Sam Asghari are "so excited to celebrate" her special day following the termination of her decade-long conservatorship.

Britney and Sam are currently vacationing in Mexico, where the insider says the couple are having a "huge celebration."

"It's the first birthday where Britney doesn't feel like she's just withering away," the source says. "This year, they're happy to celebrate Britney getting older because she's finally growing into her true self."

The insider adds of the pop star, "She finally feels like she has purpose and Britney wants to celebrate that to the fullest."

According to the source, Sam is "going all out on gifts for Britney" as the couple "want to completely live it up and not be low-key about it."

So, what does a celebration fit for the Princess of Pop look like? Britney gave fans a glimpse of just that on Tuesday when she shared a video montage from her tropical getaway, which began with a large balloon display wishing her a happy birthday.

Britney Spears Through the Years

Set the a remix of Madonna's "Frozen," the 29-second clip also showed Sam popping a bottle of champagne on a private jet, an elaborately decorated cake in the shape of a "B," a mariachi band welcoming Britney to her birthday festivities and a nighttime fireworks display.

"I'm so blessed and grateful !!!! Tears of joy today," Britney wrote on her Instagram. "Thank you for all the b-day wishes !!!! Psss I didn't even drink the champagne no lie !!!!"

In another post, she quipped, "I'm not turning 40 … I'm turning 4 and if any of you haven't HEARD … I did almost 250 shows in Las Vegas for 4 years and went out twice !!!!"

Britney added, "With that said … I think I will have to put on my hot little dresses on every night for the rest of my life to break even for working for my family my whole life with only old songs permitted !!!"

Britney's 40th birthday comes almost a month Los Angeles County Superior Court Judge Brenda Penny announced the termination of the Grammy winner's conservatorship after 13 years. The ruling was made without requiring Britney to undergo medical evaluation, and all parties involved consented to the decision. At the time, the "Stronger" vocalist called it the "best day ever."

She later described the end of her conservatorship as a "victory," telling fans, "I'm celebrating my freedom and my B day for the next two months !!!!!!!!!!!"