There is plenty of fish in the sea- This is a term commonly used when telling someone that there is many other options (people) available, so don’t stress about any one individual. America is the land of opportunity and this metaphor reveals that our society values opportunity and having/exploring plenty of options.
Break a leg- In english this idiom is used to say “good luck.” I think it is a playful expression used for performers out of superstition. This shows how our society holds some superstition amongst performers and even athletes, even though superstition is not a major part of American culture.
A heart of gold- This expression is used when describing someone who is kind- hearted, sweet, and good natured. It is comparing someone’s heart (personality) to gold (a very expensive and precious element). Comparing someone’s personality to gold shows our societies value on wealth and how a good-natured person is unique and to be cherished.