A number of practices and techniques are available to help you loosen the grip of any type of anxiety-driven, unproductive thought pattern. Since I'm not a technique-oriented therapist, I often learn from my therapy clients what works, rather than the other way around.
One woman, Katy, tells me about a technique for managing her unwanted judgmental thoughts about herself and others. She learned it from a woman's magazine she came upon at her hairdresser's.
The article suggested a "rubber band technique" for stopping thoughts. Katy has elaborated on the technique, using her imagination and self-knowledge to create a tool that works for her.
Here's what she does: When Katy finds herself drifting into negative thinking, she snaps a rubber band on her wrist and says to herself in a spirit of playfulness, "Hello again, you silly little critical thought! How are you today?" If she's alone, she may say this out loud. Then Katy puts the thought in an imaginary red dumpster and lets it ride down a railroad track where it gets dumped into a pile at the end of the track.
She doesn't try to stop the thoughts (which is impossible), but she's found a way to say howdy to them, and to use her wonderful sense of humor to give each judgmental thought--these days focused on her "loser brother"-- a little welcome and sendoff.
Katy doesn't think too much about why her brain wraps around "negative thinking" at one point in time and not another. Her belief is that the variations in her thought patterns have more to do with the vicissitudes of her "weird brain chemistry" as she calls it, than anything psychological that she needs to attend to.
No matter. Katy has a gift for silliness, and practicing this technique, combined with daily aerobic exercise, has so far offered her the best relief in loosening the grip of unwanted thoughts.