Sardonic smiles

There was this part in a book about the Kennedys, which was written by a famous author, whose name I have forgotten ( Ben Bradlee just remembered). 

Anyway, Jack Kennedy was said to have said that his younger brother had not learned how to smile sardonically. 

People tend to notice that I don't smile enough to suit them, so they come at me with that criticism.  I resent it, you know.  But you have to learn how to deal with criticism.  One way could be to learn how to smile sardonically.  Which means a fake smile, which I hate.  But I don't like the criticism too, so I won't feel that I am violating that rule.  I can smile sardonically.  Like Teddy, I just don't know how to do it yet. 

Then I thought of this deleted scene from the Terminator flick with Arnold Schartzenegger.  The Terminator doesn't smile enough, so John tells him to smile more.  Now, this is a sardonic smile.