I've noticed my self esteem varies. In general, I've been able to bring my self esteem up much higher. I did this mainly by not comparing myself to other people anymore. Whenever I'd have a thought about so and so has more money is more beautiful etc. I'd just stop the thought and remind myself that I am unique and I just need to be myself. Eventually I stopped comparing myself and I feel a lot better about myself.
Listen to your self-talk. Many people tell themselves "you are so stupid, etc" this is often from "tapes" that are in the brain from our past. Life is tough enough, there's no need to beat yourself up. Meditation can help. Look at your accomplishments.
Hope those help.