You, Zuko, and Katara all went together to beat Azula, you and Katara were watching Zuko fighting his sister, who had gone completely insane, the fight had paused momentarily,

“No lightning today? What’s the matter? Afraid I’ll redirect it?” Zuko yelled to Azula.

“I’LL SHOW YOU LIGHTNING!” She yelled back to him, before preparing to shoot a lightning bolt, she noticed you and Katara with your gaurds down, and decided to shoot at you instead.

Zuko saw what Azula was doing and jumped infront of the lightning, saving you two.