I do feel that self-esteem can be regained, after an MS diagnosis. Physically, and mentally, it is possible to get that self back. Emotionally, yes, you can feel yourself, again; will you ever be the same, you ask?
To me, that's a loaded question/statement. There are things, we go through in life, that we'll be ourselves, but a shift in perspective on life's world views, does change. It's a period of growth, in many ways.
I agree, that working every angle of this illness, can be beneficial, that includes the psychological aspect of MS. Depression can be a part of the illness.