Do not fight your thoughts. Change the way you look at them.
Sit comfortably.
Feel gravity: let your weight drop into your feet or the seat. Feel your weight being held by the seat or the ground.
Wait for the next thought, as you would wait for a sound.
When it comes, give it a label: "thought", "story" or "worry".
You do not hold it, you do not push it away. Notice how it leaves on its own.
Come back to the weight of the body and wait for the next one.