How to Stop Catastrophic Thinking After Being Triggered?

What advice do you have for catastrophic thinking after getting triggered by something? Sometimes I will come across things that make me imagine myself ending up in the worst scenario and going through the same thing another person has gone through. Example - if I read about a celebrity who shares a medical condition with me and find out they ended up in an emergency situation/almost died/etc. I think the same thing will happen to me and freak out. I automatically start imagining myself running into a similar situation and start panicking about the future. I know it's probably better not to read too much negative health stuff on the Internet to begin with but sometimes I run into it without meaning to (like when it happened earlier today, I was reading the Wikipedia article of a celebrity and it was in their Personal Life section). I just hate how my brain makes me think the worst things are going to happen to me and can't stop my fear/panic from taking over.