I've been dealing with this problem for as long as I can remember. I had negative thoughts because during my childhood I went through a 3–4 year phase of low self esteem. In college people were very nice to me and I was popular too but the self esteem problem continued which eventually led to negative thoughts. And it got worse.
Steps you should follow that I followed:
- Know what is building up the negativity. Write it down but first address that negativity. Talk to yourself. Became a selfish person and make every possible move to tackle that thing.
- People can be fooled as long as you are confident. That's the trick. Be a person you yourself never thought you would be, even if those negative thoughts are killing you. In the first few days, you would struggle with the dual personality but once you realise that people don't care unless you make a big deal out of it, those thoughts would slowly wear off. I was so negative about things, a lot of people actually commented on that when I was in college. But once I dealt with it no one said a word. Why I'm talking about people is because everyone has a problem but sometimes situations make it worse and most of the times people. You know better which of the two is doing it.