Although it is written for the musical The Waitress' leading lady Jenna, it can be relevant to anyone. It is about looking back and reflecting on how you used to be and how life has changed you, whether be for better or worse.
The first verse is referring to how she has lost herself and possibly given up on her dreams. The doesn't recognize herself in her, presumably, work uniform, a job which has taken more from her that it has given her, including not only her time is also possibly her drive and dreams. And although she was 'never attention sweet center', what she has been through has changed her, and she is not the same girl she once was, the girl she still remembers but si losing grasp of.
The chorus is saying how she wasn't perfect, but she was trying and a good person at heart, even though her actions may not have always reflected that. She is broken and won't ask for help even though she needs it, and this is slowly wearing her down. She was all things good and bad mixed up like a pie; a clean, pristine outside while the inside is a complex layering of different values and actions. She isn't the same she once was, but she still remembers those times and longs for the simplicity.
Verse 2 explore how her life isn't the way she imagined it would be. Life came up from behind and molded a person she hadn't imagined, leaving with a memory of who she was and wanted to be. Honestly, if given the chance, she would go back change what happened. A chance to start over and rewrite what happened, so she would still be the girl she wanted to be.
The second chorus describes girl that would take risks, going after what she wants. Someone who can get back up and be stronger after being knocked down. Who doesn't need anyone to love her to be herself, even though she may get hurt or scared either way. Someone that would embrace the life inside her, growing stronger each day, and keeps on fighting to be the person she dreamed of being with the fight that she once had but is now gone.
She is realizing who she was and realizing that still in herself, how she may not be perfect but she is still trying and keeps growing to who needs to become, without forgetting who she was and what she's gone through.