Nathaniel Branden has some really good stuff on his site here for Self-Esteem: Sentence Completion I: Nathaniel Branden

Its somtimes just a combination of different factors that add up to lead to us feeling the way we do.

He says the six pillars of self-esteem are:

Self-Awareness
Self-Acceptance
Self-Responsibility
Self-Assertiveness
Integrity
Purpose

And how living abiding to those will really assist one and that there's easy ways to increase in each one and learn and uncover more about ourselves through doing "sentence stems". Write 4-5 endings of each sentence to complete them:

If I am more accepting of my anger…
If I deny and disown my anger…
If I am more accepting of my sexuality…
If I deny and disown my sexuality…

If I bring more awareness to my life today…
If I take more responsibility for my choices and actions today…
If pay more attention to how I deal with people today…

Self-responsibility means…
If I take 5 percent more responsibility for my life and well-being…
If I avoid responsibility for my life and well-being…
If I take 5 percent more responsibility for the attainment of my goals…
If I avoid responsibility for the attainment of my goals…

Are just some examples. His website is good though, check it out!