The male tween tested me on a testy day while we were all at soccer practice (all of us, mind you--4 kids and me for 1 1/2 hours of practice). He was asked to please carry a basket full of toys (mostly legos and dinosaur figurines) to the bleachers. We were there for his practice after all, and I had to keep the other 3 occupied during that practice.
After an exhaustive "it's SO heavy" snide remark, he ended up walking an extra lap around the track, carrying the basket of toys.
His coach pulled me aside later and asked why #1 was walking around the track carrying a basket of toys when he was supposed to be on the field. I said, "he's learning that he's alot stronger than he thought he was."
You know, sometimes kids complain about things being "so heavy" or "so hard" when they just don't believe in themselves that they can do it. We as parents shouldn't always rush up to help them with the task, sometimes we have to let them accomplish it or even ask them to accomplish it + a little bit more.
Then they can look at their achievement and be ready for the next task with a "can-do" attitude...hopefully. :)