As an adoptee I've struggled a lot with low self esteem and self worth, nowadays my self esteem is much better it's almost great - while I still struggle with self worth issues. Self esteem and self worth is not the same thing by the way.
Here's what I'm trying to teach myself these days ;
I am worthy of love - my will matters , I should listen to it and live by it. I should stop to treat myself badly by neglecting and ignoring myself. I deserve nothing but the best, because I'm worth it. My opinons matters to me and the people who are kind to me.
For me as an adult adoptee it has proven very difficult to relearn some of these preselected assumptions because as adoptees society tries to tell us that we're useless , don't deserve the things we have or the life we choose to live and that we should be grateful towards (our new parents), that we must be grateful for the new life we got instead of the one we left or never got to experience. And if I do feel anger towards my parents its not horribel it's alright and I need to accept it and move forwards and eventually forgive them.