N.W.
When I was little we lived in Michigan and it was just the style that people would drop by. As kids we loved it and honestly it didn't seem to bother my parents at all. Now that we live in colorado that doesn't seem like the "right" thing to do. I miss it! You should look at it this way if they are your friends and they are willing to drop by un-announced then they are also willing to take the good with the bad. They want to spend time with you even if your house isn't perfect or you aren't feeling that well. Really when you aren't feeling well isn't that the perfect time for a friend to stop by and lend a helping hand. Most likely they would be willing to help you if you are down and out and they don't want to be a burden. As when it was us we weren't expecting to be entertained most of the time we wanted to just be together. I don't think a lot of people see that or get that...maybe it is still the same in Michigan but I don't know. I'm going through a tough time right now and sometimes it would be nice if my friends would just come by instead of calling because then I blow them off when deep down I know that I shouldn't.
They are your friends and just remember they love you just as you are and you just accept them just as they are. If you are heading out the door they won't be mad they will just come back again. Good friends will always come back.