To blow it

Context #1 

Jim: So how did you do on your driving test yesterday?

Harry: Oh man, I totally blew it!

Jim: What happened?

Harry: I accidentally ran through a stop sign, so I failed it.

 

Context #2 

Kathy: I have that big job interview later today.

Sara: Good luck!

Kathy: Thanks, but I'm so nervous! I hope I don't blow it

Sara: Relax. I'm sure you'll do fine.

Meaning: "to blow it" is used when someone makes a mistake that leads to failure.

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