Lyric discussion by swayness 

Cover art for Red Belt lyrics by Tegan and Sara

to me this song is about being afraid someone will repeat their mistakes I think it's about everything that's going on in her mind when she's alone and she's imagining what might be happening while she's not there. The 'red belt', i think, is a form of self protection - like in martial arts - trying to protect herself from the thoughts that keep creeping in. That's just my take on it.