bottle out

US /ˈbɑː.t̬əl aʊt/
UK /ˈbɑː.t̬əl aʊt/
"bottle out" picture
1.

to lose one's nerve and decide not to do something

:
He was going to ask her out, but he bottled out at the last minute.
Don't bottle out now, you've come too far!