Kelly Clarkson has yet another reason to celebrate this holiday season. Just a day before the “Miss Independent” singer is set to hit the stage in LA for “VH1 Divas,” she announced to fans that she’ll soon be Mrs. Blackstock. “I’M ENGAGED!!!!! I wanted y’all to know!! Happiest night of my life last night!” Clarkson wrote in a tweet on Saturday evening (December 15). She went on to gush about boyfriend Brandon Blackstock: “I am so lucky and am with the greatest man ever.”The typically private Cla