Katy Perry Grammys 2015 Performance of "By The Grace Of God" Was Stunning. Katy Perry is a musical goddess! The pop-star delivered yet another amazing performance at the 2015 Grammy Awards — she sang ‘By The Grace Of God,’ a song written about her break up with Russell Brand, and we had chills the entire time! Click Here To Watch Katy Perry Grammys 2015 Performance: http://www.billboard.com/articles/events/grammys-2015/6465629/grammys-2015-katy-perry-performs-by-the-grace-of-god