Most of us humans have times when we are incessantly thinking without any benefit. Many times these thoughts only bring anxiety with them. Often these thoughts may even be insulting to ourselves and damaging to our sense of self-worth. Here are two ways to alleviate the suffering caused by incessant and/or negative thoughts: 

A more long term way

Practice introducing counter thoughts.

My mind: "You fucking piece of shit" (a common thought if I feel i disappointed someone, or didnt live up to my own standards)

New counter thought: "I am just human and thats just fine"

This is more of a long term solution because for me it is difficult to do this in the moment of the original event that triggers the thought. It is easier to do later when the thought comes up again and I am thinking about an event in retrospect. 

Also this technique is meant to build up more positive habitual thought patterns, which takes time

The short term solution

Practice presence

This is my favorite of the two and was mainly introduced to me by the book The Power of Now by Eckhart Tolle.

This means to focus on the present moment. This doesn't mean to suppress thoughts but instead to let go of them and focus on the present. Treat your thoughts as clouds passing in the sky. Let them go by, and don't get caught up in them. 

While i'm doing meditation to practice this I like to focus on either my breathing as part of the presnt moment or focus on one or two of my senses. When a thought comes, i let it pass through. I don't get caught up in judging the thought, and then judging the judging thoughts. I gently bring my focus back to the present.

Deep brething and an upright posture can help as well