Honestly, I used to find that my negative attitude was the ONLY attitude. I was a terrible cynic and I felt that every bad idea I had about humanity was right. But I had to change that way of thinking, it wasn't overnight. When I started to see the glass half full, then I started to see the good in this world and in my life. That was step one to rebuilding my self-esteem, being positive. It wasn't easy though! It takes practice and perseverance! Daily meditation, yoga and also reading motivational quotes and texts were the best thing to help with that.
Time also is necessary because you have to learn to forgive others for how they treated you. It was drilled into me for most of my life that I was stupid and ugly and would never amount to anything. I also had bad romantic relationships that messed up my self-esteem. I realized that by holding on to all that hurt, I was still hurting myself. Forgiving isn't letting people get away with stuff, it's making an effort to move on from it and not let it affect you anymore. That also takes time. I read that if you can somehow find compassion for the person who hurt you, you can forgive them. After you forgive the others, you have to forgive yourself for whatever you've done in your life to make you feel like a bad person
After I changed my attitude and inner-voice, and did my forgiving, I started to work on myself. I made a list of all the things that were negatively affecting me and got rid of them. One was diet, I changed that completely. One was sloth, I started to exercise daily and lift weights. Another was television, it made me terribly lazy, so I got rid of the cable and my tv. With all that extra time, I was forced to fill it, so I developed some old hobbies that I'd lost interest in, knitting, sewing, cooking, playing piano, reading and writing.
I still have my days when I feel low about myself, but when I truly look in the mirror, I'm pretty pleased at the progress I've made to change the way I am, and that automatically boosts my self-esteem.
I think the main philosophy that I've created for myself, one that helps me tremendously, is that I want to look in the mirror each night and be proud of the person I am and proud of how I spent my time. This kind of forces me to be positive and to do things to make myself a better person. When you feel good about who you are, your self-esteem goes along with that.