There is a very thin line between having self-esteem and going to other extreme and just thinking that you're better than everyone else. 

This is a line that we have to be aware of and watch out for. What is the difference?

Selfishness is only worrying about yourself, without caring for the sentiments of others. The mentality of "me first". I'm more important then anyone else. I don't care what they think about me or what happens to them. I won't be happy until I get what I want.

While self-esteem is also first thinking about yourself but in the sense of believing in yourself, believing that you can achieve your goals regardless of what others think or say about you, but it's also realizing that this isn't above the love we should have for others. As a matter of fact , you can even use your self-esteem to help others and lift others up. 

A selfish person has no interest in helping others but himself. A selfish person says, I don't care what other people think about me, I only care about myself. 

A person with self-esteem says I don't care what other people say about me, my worth is not on what they say but on who I am as a human being.

Selfish people don't do anything for society while confident people contribute to the formation of society. Or they only help people that can give them something in return, even when they are helping others is really all about them.

Having self-esteem is helping others because you know your worth, you know that your valuable to society and that you can help it get better. But helping society begins with yourself, look inside you, how can you contribute to society. How can you be of help to others.

A person with self-esteem helps people expecting nothing in return.  

Everyone has something to contribute, don't say to yourself or convince yourself that you're worthless because it's not true. Society needs your help and your existence because what you are and what you have in you is worthy. This is the truth.

So don't only think of yourself and your self interests without caring for the interests of others. This is not self-esteem this is selfishness.

Helping others will also build your self-esteem because you will feel good about yourself afterwards and you will feel like you really can be a contribute to society and the to life of others.

Love God, Love Yourself, Love Others