How to deal with the anger and depression post emotional absue?

Long story short I was in a short but very toxic relationship. Verified from a specialist I am seeing, the things this she did (my past partner) was very emotionally abusive. I regret not standing up to her and letting it slide. While in the relationship, I showed it didnt visibly affect me. The day my ex discarded me, I also didnt show any signs and didnt give her the validation.

Yet, almost a year later, I am still holding resentment of the situation.