Be honest: if someone bossed you around all day, you wouldn't want to listen to them after a while, either. It's no different with children; they have their own opinions and desires and they get sick of being told what to do all the time. The key here isn't what you say but how you say it. Word demands in a way that sounds like a suggestion, create simple tasks into games to increase motivation, and perhaps even make the situation seem like the child had the idea himself.