I think the song is about running into an ex 17 months after the break up, and the feelings of bitterness and resentment and insecurity that come from seeing him. I get the impression he underminded her throughout their relationship, and seeing him when she's "on top of her life" makes her revert to feeling useless and worthless again. That's why she's telling herself to not worry or panic by his presence and to keep looking ahead and do her thing. She won't let him hold her back anymore or let her feel bad about herself.
I think the song is about running into an ex 17 months after the break up, and the feelings of bitterness and resentment and insecurity that come from seeing him. I get the impression he underminded her throughout their relationship, and seeing him when she's "on top of her life" makes her revert to feeling useless and worthless again. That's why she's telling herself to not worry or panic by his presence and to keep looking ahead and do her thing. She won't let him hold her back anymore or let her feel bad about herself.