How many times have you doubted yourself ? It happens with everyone. Let's try to overcome self doubt with the help of a simple story :
Let me tell you about the achievements of my brother who first considered himself to be fail. During the school times, he studied hard but never get a prize because he didn't have a enough confidence to write and speak well. He got disturbed by this failure.
He continued to doubt himself that he can't do anything in his life, even his friends and family started to tease him. Then he started watching the interviews of UPSC candidates on YouTube and started developing confidence. He tried to give answers to the teachers and got the position in examinations too.
After the college, he appeared in the government exams, and everyone said that don't waste time you cannot clear the interview. However, he had given the first govt. exam in his life, and the surprise came after when he had cleared the interview. Everyone was shocked even his parents.
He got the achievement because he didn't doubt himself more. he overcome his doubt and gained the success.