What's your biggest world-building faux pas?

I've come to realize recently, that you don't always need to make sense. Sometimes it's better to just leave things to the reader's imagination, so that you don't give away all your plot points. But I still think that even things which don't necessarily make sense, should make sense in the context of your world.<br><br>However, I've recently realized that the biggest faux pas you can make, is not being consistent with yourself. Let me give you an example.<br><br>So I was brainstorming for a story, and decided that a certain animal was intelligent enough to use a language of clicks and chirps to communicate. Now this made perfect sense in the context of the world, because they were semi-aquatic, and were more closely related to dolphins than cats or dogs. So a language of clicks and chirps seemed fitting. <br><br>But then it hit me, why not give them a written language as well? Now the first thing I thought of, was a language of signs, like American Sign Language. But I wanted to do something different, so I decided on a series of clicks and chirps, that could be recorded, and read like a language. <br><br>Now this made sense in the context of the world, but then I started thinking... how would these intelligent animals be able to record their language? That's where I made my biggest mistake, and that is, I had them record it with sound-waves. Now you may be thinking, what's wrong with that, but hear me out. Earlier I established that their language consisted of clicks and chirps, and was based on their semi-aquatic nature. But by giving them a written language based on sound-waves, I basically threw that out the window, and went against what I previously established.<br><br>So what did I learn from this? That sometimes, you need to let things go. I could have easily changed their language to be based on signs, or something else entirely, but instead I tried to power through, and made a mistake. So if anything, I learned that sometimes, you need to be flexible and let things go, or you'll end up with a world that doesn't make sense.