‘Write kindness in marble; your injuries in dust.’
Persian proverb.

Q. ‘I often find myself thinking negative thoughts. What can I do to stop having them?’
Applying the keys in this book will, over time, allow you to have fewer negative thoughts. Meanwhile, trying to control our thoughts (and feelings) is problematical, because they come to us unbidden. Rather than stopping them, let’s first accept them and listen to what they have to say. (Let’s label them.) Then we can ask them to leave, by any of the following methods:

Method 1. Retract your negative thoughts and statements.
Retract it whether or not you think it was an accurate thought to have. For example, if you say to yourself (or say out loud to someone),
‘Gosh, I’m stupid.’
‘That person is so stupid —’
think to yourself, or say out loud, ‘I retract that.’
‘Gosh, I’m stupid – No, I retract that.’
‘That person is so stupid – Wait, I’m being judgmental again. I retract that.’

Retract these winey expressions as well. They undermine you.  them, or rephrase them to be accurate.
‘Things never turn out well.’
‘I’m never lucky.’
‘It always happens to me.’
‘Typical.’
‘You never —’
‘You always — ’

A simple retraction is enough, but if you wish, rephrase the complaint to make it accurate.
‘Things never turn out well.’ ‘Things haven’t turned out well in this instance.’
‘I’m never lucky.’     ‘I wasn’t lucky in this instance.’

When we habitually describe a situation accurately (and therefore, without the unnecessary negativity) we become less harsh with ourselves and with others.

Method 2. Remind yourself that it’s normal to make mistakes, and you are allowed to make them.
‘I retract that. I am not an idiot; I made a mistake and I’m allowed to make mistakes.’
‘I retract that. He isn’t silly; what he said was silly. I say silly things sometimes. We all do.’

Method 3. Use imagery. For those of you who can think in pictures, try this: If you catch yourself having a negative thought, stand where you are and then walk away while visualising the negative being left behind. Or, ‘paste’ the thought onto an imagined cow (or a missle) and shoo that cow away. Do it every time the cow blunders in (every time you have that thought).

‘Think of your thoughts like pop-up ads on the internet that might be a nuisance, but you don’t have to buy what they are selling.
Unknown.

‘By making the comment come from a cartoonish outsider instead, it makes it easier to say “No, that isn’t true and I refuse to listen to you.”’
Unknown.

Method 4. Remind yourself that your negative thoughts are only one aspect of your personality, so don’t attach significance to them.

‘Thoughts about yourself that are dark, brooding and negative are a part of you, not the whole. Don’t allow these to define who you are; it’s an untruth to yourself if you do. Every person is a contradiction and a mixture of light, shade and dark and we each spend a lifetime balancing these aspects of ourselves.’
From the Wikihow site.

Method 5. Honour the part within you that doesn’t believe you are bad.
If you find a part of you that sticks up for you, support it. Honour it. It needs your support.

Method 6. Look for your deeper concerns.
‘Why do I feel anxious about being unproductive?’
‘What precisely is it about dogs that I fear?’
‘Why do I often imagine arguing with my boss? What is my deeper concern?’
‘Where do my racist thoughts come from? What is it that I fear? Or resent?’
Discovering your deeper concerns will loosen their hold on you.

Method 7. Be angry with yourself, but in a healthy constructive manner.
This tip has its own chapter, ‘Be Angry With Yourself‘. In short, you have every right to be angry, but find a healthy way to express it. No self-blame, no self-insults. You will fulfil the urge to be self-critical without actually being self-critical.

Other methods:

‘When you have a negative thought say to your brain: ‘Poor brain, you’re frustrated,’ or  ‘Goodbye, Thought.’
(From Dr Harris in his book, ‘The Happiness Trap’.) This suggestion was in the earlier chapter about dealing with emotional beliefs. It’s here as well because it’s good for dealing with all negative thoughts. Here’s a reminder:
In the same way you say goodbye to your disabling beliefs, say goodbye to your thoughts:
‘Here’s that thought about me being bad. Hello thought. Goodbye.’
‘Here comes the “I’m the victim” story. Hello story. Goodbye.’
‘Hi thought, see you later.’

A suggestion from Amanda McClintock: ‘. . . one of the best things I found was this one lesson, this one week, and I can’t even remember what it was called, but it was fantastic. Basically, I had to pick a thought that . . . would go through my head all the time. And that one thought for me was “I’m not worth it. No one wants me here, I’m just not worth being here.” During the next week . . . every time that thought would come into my head, I had to sing it. Like, say it in a silly voice, put it in an accent. I had to draw it on a piece of paper and put decorations all around it so it looked like a “Happy Birthday” banner up. I had to sing the words “I’m not worth it” to “Happy Birthday” or “Twinkle Twinkle Little Star”. It made the thought sound ridiculous. It made it sound like the most ridiculous thing on the face of the earth, so it makes you laugh. . . . “Why would I even think that? It’s just not true.” Putting it in that ridiculous sense made it seem so much less of an issue.’
From the SBS television program, ‘Insight’, with presenter Jenny Brockie. 29th March, 2011.

‘I would just play devil’s advocate with my own thoughts. “That’s rubbish, that’s ridiculous.” Sometimes I would say things out loud to myself or just do something to interrupt that thought pattern so I could then move on and that fear would dissipate.’
Kate Warner, from the same Insight program.

‘Force yourself to concentrate on something else until the urge passes.’
Guy Winch.

‘When a person becomes unusually depressed about an event in her life, it’s often because of three mental distortions: (1) she feels that the situation is permanent; (2) she feels that it is critical, meaning that it’s more significant than it really is, and (3) that it is all-consuming, that it will invade and pervade other areas of her life. When any or all of these beliefs are present and elevated, it will dramatically increase her anxiety and despondency. Conversely, when we think of a problem as temporary, isolated, and insignificant, it doesn’t concern us at all. By artificially inflating or deflating these factors in the mind of another, you can instantly alter their attitude toward any situation, be it positive or negative.’
David J. Lieberman, in his book, ‘Never Be Lied To Again.’

So, you have a heap of methods to choose from. Choose one and give it a go!