Answer:
In a jam:
I will be in a jam if Peter doesn't pay me back by tomorrow.
Had she not thought to carry an umbrella that morning, she would have been in a jam.
Got cold feet:
Mary was supposed to play Juliette in the play but she got cold feet at the last second, so her understudy had to play the part instead.
I wanted to go skydiving, but I got cold feet when we went to sign up.
Explanation:
To be in a jam means to be in a spot of trouble, or a tricky situation.
To get cold feet is to feel too frightened to do something you had planned to do.
