Right, lots of people have felt depressed too. That doesn't mean they've got clinical depression. It is clinical when it is so extreme that it impacts every facet of your life.
Think of it this way: lots of people can't see well, but not seeing well doesn't mean blind. If you don't see well you can improve your life by wearing glasses. If you're blind glasses aren't going to help. The whole way life functions revolves around dealing with being blind. There are all sorts of things you'll need to do to cope with blindness that people who aren't blind, or simply don't see well, don't have to do or think about. So it isn't quite right to equate not seeing well to blindness, even if people who don't see well can imagine what not seeing at all might be like since they can partially experience not being able to see.