get cold feet
US /ɡɛt koʊld fiːt/
UK /ɡɛt koʊld fiːt/

1.
avoir froid aux yeux, se dégonfler
to suddenly become too frightened to do something you had planned to do
:
•
He was going to ask her to marry him, but he got cold feet at the last minute.
Il allait lui demander de l'épouser, mais il a eu froid aux yeux à la dernière minute.
•
I was going to try bungee jumping, but I got cold feet when I saw the height.
J'allais essayer le saut à l'élastique, mais j'ai eu froid aux yeux quand j'ai vu la hauteur.