Mercury in Cancer uses an emotional approach to thinking, how thoughts feel is equally as important as cool reason and logic.  This Mercury is intuitive, sensitive, an expert at detecting subliminal emotional undertones in seemingly benign conversation.  They know what you are NOT saying.

Mercury in Cancer has an uncanny talent for influencing people, their power to sway the public is due to the lunar influence.  Conversely, this is a Mercury easily swayed by emotional sympathies.

Refer to natal moon phase; obviously note moon phase by transit to work this natural instinctive ability in your favor.

Mercury in Cancer has feelers out 24/7 testing concepts and ideas brought forth via emotional intelligence, they learn by watching, feeling the situation.
Cancer is a sign that cares and nurtures – thoughts are no different.  If ideas set off good emo radar, they are more likely to stick; irritating ideas are quickly jettisoned for the same reason.

Logic tends to takes a backseat unless this tendency to emotional investment is recognized – especially re: matters close to home.