J.B.
No I feel that way too. But while you're looking around thinking "I don't know how she does it..." someone is thinking the same of you.
Here's what I've come to realize - the real power players have help and lots of it. Cleaning ladies, nannies who come to the house, personal trainers and lots of take out dinners. I have friends like this, and this is how they function. Sounds nice, but usually there's a downside - like longer hours, or travel - to the upside, which is higher pay to be able to afford more help. One of my sisters owns her own interior design business. Her husband is a corporate attorney who writes books (which are published) as a hobby. They are beautiful, wealthy and she is always put together, because that's what her job demands. But she literally has three nannies (a day nanny, a night nanny for her newborn and a weekend sitter). Groceries are delivered, the cleaning lady comes once or twice a week. I wouldn't trade places with her for anything. There are a few female executives where I work and while they love their jobs and their lives, the trade off is that they miss out on a lot too. Different strokes for different folks.
The only friend I have at work who never slowed down or appreciably changed her life when her kids were born regrets it because her kids really dislike her. Lots of family issues. Everyone else I know has slowed down during the baby/toddler/pre-school years, so that's another thing to keep in perspective. The ones who are bright-eyed and knocking it out of the park at work probably have kids who are a little older than yours, and that makes a huge difference.
I often feel like a failure too, and I've got 4 kids, a demanding FT day job and a seasonal tutoring/teaching job evenings and weekends. I hear a lot of "OMG how do you do it?!" but I'm usually looking at the other mom and wondering the same thing. Remember that we're all in the same boat, really.