I read this description of what it feels like to be sick and not necessarily look sick. I think it's a good way to physically demonstrate the concept to people who are genuinely interested/curious about what it's like to not be healthy. I don't need people to realize that it is a big deal when I can spend time with them, but I think it'll be nice for them to know that when I spend time with them, it means they are special to me.

http://www.butyoudontlooksick.com/2004/11/the_spoon_theory.php