The hatred you're feeling towards your mother is what's known as a secondary or 'cover' emotion - we humans tend to get caught in such surface emotions (anger, resentment, hatred, bitterness, etc. - ie all forms of negativity), and we find it very difficult to feel the deeper, more vulnerable feelings of, for example, grief and hurt (this tends to be more difficult for men, I suspect). I've struggled to let go of such feelings myself; I've found that becoming more sensitive in the body and allowing it to relax and gradually release both the surface emotions, and also those deeper feelings that the surface emotions are unconsciously designed to keep at bay, is what's required. It can be a bumpy ride, but I think it's necessary to do that inner work in order to let go of the negativity you're feeling.