I think it’s using a muscle which, with practice, strengthens. The bad habit of negative thinking can lesson with each time the muscle flexes to replace the bad thought with a good though. For negative self talk, telling myself I am bad essentially, I try to stop and remind myself I am good. I have a DBT workbook, and will open it to any random page and start reading when in spiraling negative thinking now sometimes. I really have to fight my inclination to go down the negative self talk spiral and, of course, feel better when I can put myself on distracted better footing.