[speak] too soon
1
to say something that is very soon proven wrong or inaccurate
The idiom "speak too soon" originated from the idea of prematurely expressing an opinion or making a confident statement before all the relevant information or events have unfolded. It is used to suggests that the speaker's statement may be invalidated or proven wrong by subsequent developments.
- I think we're going to win this game easily.
- Looks like we're going to have a quiet day at work.
- I'm sure the problem is fixed now.
- This new diet is so easy, I'm already losing weight.
- I don't think it's going to rain today.