I think what mindfulness does is what CBT is often trying to do, which is to help us recognize our patterns of thought that can be like habits we have learned, including such thoughts and feelings as self-hate. The difference is that it is done through directly experience rather than writing things down. Like mitz says it is experiential. Just doing this can help us to see that these thoughts and feelings do indeed come and go. Instead of fighting them, we try to acknowledge them with compassion towards ourselves, then gently bring our attention back to a point of focus in the here and now, which is typically just watching the breath without doing anything special. You try to feel it directly, such as the rise and fall of your belly, from the inside rather than thinking about doing it. The "body scan" meditation Paula describes involves much the same, but the attention moves through the body, and is excellent for grounding in our psychical self, where we are just "being" rather than the constant "doing" of our thoughts, if that makes sense!