Vicious circle

A vicious circle (also called a "vicious cycle") is when one bad thing leads to another bad thing, which leads to the first bad thing happening again. This can go on and on and become a really hard thing to stop. Here's an example: Your friend is really sad and tells you about it. You try to cheer them up but nothing seems to help. As a result, your friend gets even more sad, so you keep trying to cheer them up but nothing works. This can keep happening over and over again and it keeps getting worse and worse.