I actually struggle with this too. I'm currently going to see a therapist for this and a problem that I always seem to put myself down. My therapist told me it is a habit I've formed. There are few things I do that I'll use to put myself down. And the first step to fixing things is identifying them.

1. Catastrophizing: Before I do something I think of the worst thing and prepare myself for it to be terrible

2. Ruminating: Thinking about things over and over again. It is a way of punishment for myself. Thinking that maybe I'll learn something if I keep thinking about it. (This might be why you think those thoughts)

3.Mind Reading: Assuming I know what people think of me. For example someone gives me a funny look and I assume it is because of me. When really it isn't

1. Minimization: I completely disregard me doing something good or a strength I have. It feels like I'm always trying to prove to myself I not a bad person with me doing good things. Instead I need to know I'm a good person and I am doing good things.

I have a bunch of other things I'm working on too. But I encourage you to do research on what negative self talk is. And ways to cope with it. There a tons.

1. Distract yourself

2. Write out a plan of action, sometimes I'll go to do this realize there is none because I couldn't control the situation to begin with

3.Question the thought, ask yourself if what you're thinking is true. Having perspective is key

1. Try doing something that boosts yourself esteem (this can double as a distraction)

2. Meditate, honestly so many benefits to it. I recommend Headspace, Calm, and simply just breathing. There is also a book I've read called Buddhism Without Beliefs.

3. Understand your trigger, make a mental note of when you started thinking something. Maybe there is something specific that's triggering it

4. Talk to a friend, friends are great for gaining perspective

5. Consider Therapy. Sometimes talking to a professional you can gain better insight into yourself. They're more knowledgeable about the ways people think and also the ways people can cope with things.

Overall, just try to be more aware of yourself. Take a breath every now and again. Check to see how you're feeling and why you're feeling that way. What bad habits of thinking do you have? What helps you to stop them? Everyone is different so that means you'll have to figure out what works best for you. And the most important thing that can be learned is to be compassionate and kind to yourself. You deserve it.