This is a song about an emotionally abusive relationship. She wants to give her partner everything, do anything they ask, be anything they need (which let's be real is pretty unhealthy, codependent behavior). The person she is singing to takes full advantage of this, pushing her away (hence the lyrics "I can stay away for days/If that's what you want") and then pulling her close again, making more relationship demands ("I can dance and play the part/If that's what you ask"). She needs to "hold the weight of worlds," being responsible for all of her partner's needs, while never criticizing her partner ("I can hold my breath/I can bite my tongue"). The lyrics "Your words in my head, knives in my heart/You build me up and then I fall apart" is about how her partner tells her she is wonderful and perfect but then in the next minute/hour/day blames her for everything going wrong, putting metaphorical knives into her heart. If you've been in a relationship like this you know how the ugly words can echo in your head for days.

As the song goes on, the refrain changes from just "I can do it" to "I can do it/I'll get through it" until finally she sings: "I can take so much/'Til I've had enough." She cannot really make everything perfect by giving all the time while her partner pushes her away, pulls her close, makes demands, verbally abuses her and then blames her for everything. She is only human. This relationship is hurting her and she can't take it anymore.

If breakup mix CDs were a thing this would be on mine.