Against The Grain Meaning

(idiomatic) Unwillingly, reluctantly; contrary to one's nature.

Example:   By going against the grain and going to work nude, you've made yourself a laughing stock.
  It went much against the grain with him
1608, William Shakespeare, Coriolanus
  Say, you chose him / More after our commandment than as guided / By your own true affections, and that your minds, / Preoccupied with what you rather must do / Than what you should, made you against the grain / To voice him consul: lay the fault on us.