Home is a sacred place. And if someone invites you to his home, you want to be yourself. Just be comfortable, be natural, but, on the other hand it's not necessarily a bad thing to be over polite. It's not necessarily a bad thing. Maybe your counterpart may feel uncomfortable because he may think that you're not comfortable enough and he's not doing enough. And if he's not doing enough, trust me, they will force you to do something. 'Eat, eat, eat, drink, drink,' even if you're done. If you don't do it, it means you're either too polite, or you don't like it.