Recently saw a comment on a blog whereas the gentleman stated to the effect that "everything had been photographed..." which practically speaking might be near true. I have even thought that same thing and remember an incident where we were traveling through a small route 66 town and wife asked me; 'aren't you going to stop and take pictures"? Guess I was tired because I stated No, why take pictures of something that so many people had already photographed. After a great meal and some coffee at the Crackerbarrel restuarant in Kingman, AZ.  I was once again ready for some photography. Because, although most everything out there has been photographed, we need to look at each and every opportunity to do it better than others have. Walk around, sit, linger, change the camera angle, wait for better light, get up earlier or stay out later in order to get "the shot" that's the "same but different" and even better.
Keep on taking pictures.