The first thing you need to do is stop comparing yourself to your sister; you'll find it much harder to achieve your goals if you're focusing your attention on her.
Envy, Jealousy and Sibling Rivalry
Psychologists suggest that sibilng rivalry is much stronger in children who are close in age and of the same gender; with twins, it can be even more intense. The thing is, when you're envious of somebody, your perception of them is warped; you see them as a representation of the things you want, and tend to overlook their flaws. There's a good chance your sister envies you in some ways.
Harbouring feelings of envy and resentment is going to bring you nothing positive, and you risk damaging your relationship with your sister and other family members. Try not to resent your sister for the way her life has turned out. This might be difficult at first, but it will get easier if you stop comparing yourself to her. Try to see it as a good thing that you influenced her, as it shows she respects and admires you.
Focus on Yourself
Whatever you want to do with your life, start taking steps towards your goal. Knowing that you're making progress, even if it's slow, will give you a sense of achievement and help you to feel more positive about yourself.