Simply stopping negative thoughts in their tracks can be helpful. This is known as "thought-stopping" and can take the form of snapping a rubber band on your wrist, visualizing a stop sign, or simply changing to another thought when a negative train of thought enters your mind.

Sometimes looking at things in the long term can help you to realize that you may be placing too great an emphasis on something. Shift your perspective by imagining that you are panning out and looking at your problems from a great distance.

Decrease it’s negativity by imagining you are saying your self-talk to a friend. If you know you wouldn't say it in a certain way, think of how you'd share it instead or what you'd like a good friend to say to you. 

Catch your negative self-talk and ask yourself how true it is. The vast majority of negative self-talk is an exaggeration, and calling yourself on this can help to decrease its damaging influence.

You can limit the negativity by setting up a maximum time for self-criticism or only allowing self-criticism to certain things in your life.

When you think of your inner critic as a force outside of yourself and even give it a goofy nickname, it's easier to realize that you don't have to agree, and it becomes less threatening and more easy to see how ridiculous some of your critical thoughts can be.

Take a negative thought and change it to something encouraging that's also accurate. Repeat until you find yourself needing to do it less and less often. 

Your thoughts and feelings about yourself can't be considered accurate information. Your thoughts can be skewed like everyone else's, subject to biases and the influence of your moods.