I am confused the usage between 'of something' and 'for something'. E.g., the difference between
the expression for freedom
the expression of freedom
the sacrifice for freedom
the sacrifice of freedom
They seem both refer to the same thing. the sacrifice for freedom seems to me that it means the sacrifice was made for freedom; the sacrifice of freedom seems to me it's the sacrificing of freedom, so both refer that they are a direct relation of freedom, it's hard to know which should use between them.
I wrote these expressions myself, because it seems to me 'expression of something' and 'expression for something' look the same. I am having hard time discerning the difference between them. Furthermore, I get confused between 'of something' and 'for something'. I am often puzzled which one should be used in specific context correctly.
So what's essential difference between 'of something' and 'for something'?