Do something then finish it. Take pride in what you are doing. School, learning a different language, maybe an instrument. I'm shooting in the dark here, cause I believe AlphaBail is right. Not enough information to give accurate and educated advise.
Start by always dressing you best. Dressing your best will always lift you spirit and confidence. Make sure you focus on the positive in your life and your looks. If people compliment your eyes, hair, hands or any part of your body, make sure you use it to your advantage.
As JoeO said, dress your best. also, just strut your stuff, insecurity doesn't look good. Walk with purpose and keep your shoulders back. Why do you care what people think? It your life, not their life
If you walk into a room and believe that your Awesome and Confident and you really believe it then other people will do. And if your a girl have a you day do what you want one day every month go to the spa ,buy a new top,get a mani or pedi , go to the movies , read a romance novel or what every book you want just be you for a day!
Take care of yourself. Healthy diet. Exercise body and mind. Help others. Spend time with family and friends. Have time to yourself. Don't neglect the spiritual, whether it's practicing a faith or having some quiet time or appreciating nature.