Negative thoughts often lead to an unsuccessful life and less confidence in you, if you are constantly worried and only thinking about what you do wrong. You think that you are not good enough; you are not going to lead a successful life. Negative thoughts are toxic and decrease your ability to perform. These thoughts might even make you avoid positive situations all together.
The best thing you can do for your health and to increase your self-confidence is to learn how to identify and change these negative thoughts.