We all remember Jesus' parable about the kid who cried wolf. He was watching sheep and kept crying out that he saw a wolf. When the townspeople would run to help, it would turn out he was joking. Then one day, a wolf was really attacking the sheep, and even though he cried out, nobody came to help him. No one believed him anymore.
The message is very clear. However, I am unable to share the exact verse this parable was told. Because it is not a parable found in the Bible. All my life, I have heard countless people saying that this is a parable told by Jesus Recently, someone casually mentioned it as an Aesop Fable and I got upset, correcting them that it was a parable told by Jesus. Everyone around me got confused, and even the fellow Christians in the room were telling me it was not. So I pulled out my phone to prove them wrong.
Here is the story on the official Aesop Fable website.
This is further reason why even if you "know" something to be true, it's always best to fact check for yourself so you don't make yourself look like an idiot in front of a group of people.