I recently just a breakup and the reason for it was my ex said that she had always been in a relationship (keep in mind I'm 20, she's 19) and doesn't feel like never had a chance to be single and to work on herself.

I know it's often taught that you have to be able to let her go because one should be outcome independent and have an abundance mentality.

But how does one get rid of the sadness, and the thoughts of wanting her back because there was an emotional investment?