maxalt, safetypee & john_tullamarine have said it all.
There is another catch: You might get away a hundred times with a “little” ice, probably not even noticing anything during your flight. But when it comes to situations requiring max performance i.e. an engine failure during takeoff, that trace of ice on your wings (and fuselage) can erode the life-saving bit of climb capability you would otherwise have had.
happy landings