A lot of people mistake self-confidence with self-esteem. I used to make that mistake as well until I started studying about believing in oneself and abilities.
From my own understanding, self-confidence is slightly different from self-esteem. Self-esteem has to do with your feelings about yourself, your behaviour and your worth as a person. While, self-confidence is your believe in your abilities and in the way you present yourself to the world. Peoples actions or reactions are more likely to erode your self-confidence than it would your self-esteem. Talking from experience.
So, these two emotions have quite a bit in common. They are both measures of your believe about yourself; yet can be easily thrown off balance, which may lead to your being overconfident or portraying behaviours that could distance you from your actual existence.
That being said, you need to find a balance between too little self-confidence and too much. You can't accomplish much without self-confidence, because truth be told, not everyone will like what you're bringing to the table. You must be confident enough to push through. Consequently, too much self-confidence can make you too comfortable and ensures that you don't push hard enough to reach your goals.
Truth is, you can do anything you put your mind to. There is no limit to the power of the human mind. Your possibilities are endless.