How can I improve my 25 years of low self-esteem?

Get out of you comfort zone every day by actually talking to girls, even if it's just pretending to but perfume from a shop girl it still a valuable interaction with a girl. Do something that's makes you proud of yourself, get fit lose weight, learn kite boarding just do something challenging that makes you feel good about you. Build up your confidence slowly and try not thinking of girls as a conquest or an unattainable prize, they are nervous too you know, most of us are at first.