I completely agree with this.
If you can't sell yourself and/or your services in a convincing manner, it really doesn't matter how much of a jQuery ninja you are.
One resource which has been invaluable to me in this respect was the BoagWorld podcast.
It might be worth checking this out. I recommend listening to the old episodes, too. A lot of the material they cover is still relevant today.
Not sure I agree with the first part of this statement, but if you run into something you can't handle with your current skill set, you can always outsource it to another developer.