Does anyone have a recommendation for resources that help in building self-worth?

I’m thinking of something along the lines of the BPD workbook by Daniel J. Fox but really I’m open to any suggestions.

I really struggle with low self-worth, perfectionism and relying on external validation to a point where it’s affecting basically all areas of my life. I’m in therapy and DBT group but I’m looking for additional resources specifically for this. 

Many thanks! 💙