Britney Spears is one "Lucky" birthday girl! The singer received a sweet message from boyfriend Sam Asghari in honor of her 38th birthday on Dec. 2. "We live, we laugh, we argue, and most of all we LOVE," he wrote on Instagram. "There's a reason why the world fell in love with you! You might be the princess of pop but mostly you're my princess. Biggest Happy Birthday to you @britneyspears." Sam also shared a throwback video from their date at an ice skating rink, which featured a cheeky nod to Britney's iconic song!