“I guess that I forgot I had a choice”

Katy Perry – Roar Lyrics on LyricsMode
EXPLANATION

Often people run through life not noticing anything around, accept their reality and step by step do not see how not begin to play their game. That's what happened with Katy Perry. And when she came to her senses, she expressed it simple and understandable stitch: "I guess that I forgot I had a choice".
EXPLANATION
She forgot that she had the courage to do anything and that she could stand up to anything.
EXPLANATION
I should note that she is using "forgot" ironically here. She hadn't used or made her "choice" for so long it was like she had forgotten she could choose. If you choose not to decide you still have made a choice.