what worked for me when I had low self esteem was to find a strength that I had and focus on that. when I felt bad and was badmouthing myself, I would tack on, but I am great at, for me it is writing. then I could counteract that negative thought with something positive. so you see someone more successful than you, you could say, yeah they are good at that, but I am good at this. then you find another strength about you until you have tons of strengths about you.