I realize that it is an unfortunate but natural part of being a woman to occasionally wish you were thinner. I'm generally cool with how I look, but some days I see a really awesome skin tight dress with a million cutouts and wish I was Miranda Kerr. That lasts all of five minutes and then someone puts a pizza in front of me and I'm me again. But I know a lot of great women who put way too much of their time and energy into thinking about how their life would be better if they were a size 2. And here's the thing: the size of your waist absolutely and unequivocally does not correlate with your quality of life.
In talking to friends, it seems to be a common belief that if they can just lose ten pounds, they'll be happy. But the problem with that is, there will always be another ten pounds. No matter how thin you get, or how good you look, or how toned your arms are, there's literally always room for improvement. So if you're placing your self-worth and happiness in that pesky ten pounds, you'll never be happy, because there will always be a couple more pounds you think you could lose. You lose ten pounds, and then it's another ten, and then it's a six pack, until you drive yourself nuts going after some crazy idea of what you're supposed to look like. You're chasing something that will continue to elude you, because the problem isn't with your body, it's with your mindset.
Think about it this way: in the grand scheme of things you want to be in life, is skinny at the top of that list? Is "skinny" the best compliment you could receive? Would you not rather be funny, intelligent, caring, successful? Try to re-prioritize what you want. Working out is good. Eating healthy is good. Obsessing over the way you look and thinking your life will only be fulfilling if you're thin is decidedly not good. Come up with goals that have more to do with your talents and what you can do, rather than just how you look.
I'll leave you with a Mindy Kaling quote, because this girl has got great things to say about self-image.