Some expressions are complex—
ingenious work of eyes and lips.
Can you guess the one
that has been with me forever?
It shifts and bends, serves many ends—
at times it lingers for a bit
before it flees,
but it always comes unbidden.
It shields me when I'm caught off guard,
deceives those who seek my tears.
It does so much and asks so little,
but above all—it contradicts.
Hint: (: