I definitely push my kids occasionally. I feel that they need it so they can learn that their boundaries may be farther out than they realized. I also think it's essential that they be forced to puzzle something out at times. My opinion is that when learning comes very easily for too long, the child is at risk for not learning how to challenge himself.
People for whom learning isn't so easy have an advantage in this regard, because working hard to get something is more familiar to them. Our school system isn't set up to teach gifted kids how to...well, struggle. There's a lot to be said for internalizing the idea that "This looks impossible right now, but if I keep trying, I'll get it."
Val