So I really struggled with stopping the negative thoughts long enough to hear my true voice. I found myself beating myself up for having them which caused more. My treatment center said to say something positive instead, but I didn't believe the positives so it seemed all fake.
So what worked for me was just responding to them with "I don't believe that any more." I didn't know what I believed but I had to stop believing the negative ones and by acknowledging them, at least I didn't beat myself up for having them. They did start to quiet down and I slowly could hear my true voice. The more I could hear and listen to that true voice the quieter and quieter the negative ones became.
I still have my moments but it's much easier now to stop myself from traveling down the negative road. Now when they come up I remind myself of something positive about myself (which is what I was told to do in the first place....just took me some time!)