There are a few for different situations: Jinx/Knock on wood: when speaking of something bad, some people will knock on something wooden to prevent the "jinx" from happening. Speak of the devil: When talking about someone, and they show up soon after. Self-fulfulling prophecy: Probably closest to your idea.
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VorparSelf-fulfulling prophecy: Probably closest to your idea. Someone worries about something, and then the worry causes the problem to occur.Thanks Vorpar, as you said It's just what I needed, but another question that pops up in my mind is that how can I use it?
virginia274My worst fear has just come true.Good.
virginia274And also, I searched in Google and I found this "Your worst fears have been realized". Does it mean the same and is it interchangeable with the previous one?I'd say so, but "realized" is more formal.