The Grammy-nominated singer, whom emcee Chris Tucker called "the new queen of British Soul," told the star-studded crowd at Cipriani Wall Street that she wrote her song "Who You Are" when she was 18, after she "had just had a minor stroke. I thought that I was never going to get better."
"I feel so lucky that I was given a second chance at life," she continued. "So every day when I am able to do this, you have no idea how amazing it feels that I'm so lucky to be onstage and singing and living my dream."
The British-born singer, 26, has had heart problems since she was a child, when she was diagnosed with Wolff-Parkinson-White syndrome, which can cause an irregular heartbeat.
She dedicated her performance of "Who You Are" "to anybody in this room who's lost somebody to cancer…"
While singing the lyrics to her hit song, Price Tag – "It's not about the money, money, money" – she quipped that "tonight it is about the money." (Indeed, the gala raised a record-breaking $4 million for Delete Blood Cancer, which will be used to register life-saving bone marrow donors.)
During the song, an ebullient Jessie J came offstage and moved through the crowd, going from table to table, singing to guests and even sitting on a couple of people's laps.
Other celebs who came to the gala included Coco Rocha, Doutzen Kroes, Kelly Bensimon, Dita Von Teese and Georgia May Jagger, who was just named the first Coty Global Ambassador in the fight against blood cancer.
For more information or to register as a bone marrow donor, please visit deletebloodcancer.org.