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.


https://languagesystems.edu/