In essence, you envy your sister. Envy is a powerful poison. It corrodes our inner self, and causes us to spill unhappiness onto those around us. But envy is also a good thing: it's a rare opportunity that you should exploit to the fullest.

Envy points towards something deep in us: a need, a desire, sometimes an ambition. Envy is very impolite in pointing fingers at our inner workings, regardless of whether we like it or not. Your envy is a tool that you should use to learn more about yourself: for instance: are you envious of your sister's beauty, or the praises that she gets, or the kind of people from which she gets that praise? These are all subtly different, and it would be good to know which of those are concerned. Either way, it seems that it's very important for you to have beauty, or to be praised for your attractiveness, or to elicit attraction from a certain group of people. Perhaps you thought you were above that, or perhaps you did not realize the strength of your need/desire for those things. Now - thanks to envy - you know it.

The big mistake would be to self-hate yourself for that need. That want, or need, is just part of what you are. It does not mean that you will always be so, but at the moment, it really is a chunk of you, and you should respect it. Think about it: do you cook meat for a vegetarian? Do you insult religion in front of your very pious grand-mother? Not if you respect and care for those persons. You should be equally respectful about yourself. You should accept certain aspects of yourself (no denial), and actually cater for them, out of care and generosity for whom you presently are. By this I do not mean that you should undergo plastic surgery, but that you should take stock of the fact that your aspect or the appraisal from others is important for you, and so devote some effort into developing your own style and appearance. Angrily reacting against that would just be a form of self-mutilation that will do you no good, and create some real self-hate.

The crumbling that you feel are the cracks in your self-image, threatened by the presence of your sister. But think again about this: why does your sister cause this? I'm sure you'll agree that there are plenty of women more beautiful or that get more praise than your sister, and it does not bother you at all. Why? Because of a form of self-delusion that continuously affects your thinking. You probably dismiss those women by some sort of rationalization. You're so used to it that you don't even notice it. But your sister is too close to you, and that self-deception crumbles. This is a great opportunity to notice the veil of self-delusion, understand how it works, and rip it apart. Don't waste it.

Nevertheless, despite all the good points of envy, in the end it's a negative force in your live that you need to neutralize. Envy is often the original cause of family break ups, don't let that happen to you. The best way to control envy is first to realize it (done), accept it (nearly there), and move full on against it. Praise your sister even if it bothers you. However it pains you, accept that she is pretty , and that people will say she is pretty. Accept that it bothers you that you are envious. By facing head on these realities, you will get used to them. In time they will affect you less and less. Actually, there will be a time when you will see this with detachment, because you have accepted it from your inner self, you do not need to force it down on yourself. By then you will have actually matured. Being able to realize and neutralize your envy before it controls you is a precious skill, it will give your character a lot of depth, because it requires acceptance of your weaknesses, but also the fortitude to deal with the fallout.