Been there, done that 나도 다 겪어봤어

I guess she’d lived life too long on her own terms. Or maybe she was afraid to get her hopes up. To trust.

I understand. Been there, done that.
323p

* on your (own) term 자신의 방식대로

https://tenor.com/bDQ5J.gif

Alvin And The Chipmunks Alvin GIF - Alvin And The Chipmunks Alvin Been There Done That - Discover & Share GIFs

https://youtube.com/shorts/ErOIHc8cdl4?feature=share

It means that you have experienced something similar and also had a similar reaction.
It would be like saying, "I understand what you mean, I have had those kind of days too."