There's no crying in baseball

[Sonia]

Taken from the 1992 film A league of their own, when Tom Hanks character says it to own his female players who started to weep when she couldnt handle the criticism he had on her.
Outside of baseball, people replace the last word with their occupation (Theres no crying in politics!///Theres no crying in wrestling!///etc)
When someone says that to you, they actually want to say something like Be a man or Dont be a pansy.
A variant of the use was spotted on many websites, while commenting on Hillary Clintons infamous speech in which she seemed to on the brink of crying.