You come up with a theory. You think that it's pretty cool. It explains something about the world that you couldn't explain before. Better yet, it gives an idea of something you can do about it. You're pretty excited.
Then you learn something that seems to poke a hole in your neat little theory. Crap. Back to the drawing board.
The world is complex. Really complex.
Any theory complex enough to fully describe a system has to be as complex as that system. So even if you come up with a perfectly "true" theory, you've gotten nowhere: you've gained no insight into the problem you're trying to solve because you haven't reduced it all. "True" implies "not useful"
So we come up with imperfect theories, and we use them.
This extends to all theories, including the most general of all: words.
What exactly is a chair? I dare you to try, but you can never define _exactly_ what is chair and what is not chair. This is because your chair theory of the universe isn't true. The universe doesn't give a crap what you sit on.
Chairness isn't "true." But like any good theory it is certainly useful! Not only does the chair theory explain what things are good for sitting on, it also tells the makers of chairs what they should make, helps you furnish a home that is comfortable to visitors, and allows concert halls to let in the right number of people.
So don't be discouraged if your theories are wrong. If it's useful: use it. And just because your words have been useful, that doesn't make them true. In fact: it means they aren't.