I believe in this world have only two thoughts, the first is “positive thinking” and the second is “negative thinking”. If you always positive thinking so many things that you will get to make your life better. But how about the people who always think negative? Negative thinking does not carry anywhere, only worsen mood, and be bad for our performance. This could be The Ring of will never see the base of the tip.

then how can I fix?
Well, some things that may help to prevent and overcome negative thoughts which are as follows:

1. Consider Living in the moment.
Remember that only the present that we can control. Do not think about the things that has not happened or had happened, and make it into the power implanted for us to live in the moment.
2. Say positive things to yourself
Tell yourself that you are able and capable. Say it over and again, any time. Especially, start the day by saying positive things about themselves and the day, no matter if the day you have to make decisions difficult.
3. Believe in the power of positive thinking
If you think positively, positive things will come and the difficulties will
feels lighter. Conversely, if you think negative, negative things will befall you. It will not be easy to change your ‘Mindset’, but worth the effort you can reap.
4. Focus on positive things
When we’re being so negative, we often forget what we have and focus more on what we do not have. Make a journal gratitude. No matter the time, each day write down five of six positive things that happened on that day. Positive things that could be big things or just little things like ‘today better than yesterday’. This could
change your negative thoughts into a positive thought.
5. Face your fear
Negative feelings come from fear, the more afraid you are going to live, the more
many negative thoughts within you. If you are afraid of something, do something. Fear is a part of life but we have the option to do not let fear stop us.
6. Try new things
Trying new things can also increase self-confidence. With say yes to your life open more opportunities for grow.
7. Change perspective
When things do not go well, find a way to view it from the viewpoint of the more positive. In every challenge there is profit, there are advantages in each challenge.

Here are some things that may help to prevent and overcome negative thoughts. I quote this from Mrs.Jessica Padykula, I just add and slightly change the words. Hopefully useful for you, if you have other ways that may help to prevent and overcome negative thoughts, please share here.