ON halfway trough
Hey there, English native speakers.
I have a Brian's Griffin phrase (from the Family Guy cartoon),
"You're right. Everything I've ever done, I've crapped out on halfway through.
Well, not this time.
I am going to finish what I started."
Honestly speaking, I know in common what he meant there, but I am still a bit frustrated about the "on" using in the phrase.
All dictionaries I use know only "halfway through" expression, but not "ON halfway through".
So, could you explain please:
a) does the Brian's saying sound correct in English?
b) what do you think you exactly mean when you use the "ON halfway through" part, if it wasn't a mistake?
Thank you in advance.