Because Geminis are so intelligent, they can be know-it-alls and unintentionally make you feel intellectually inferior.
When they hurt you, it's hard to get them to take responsibility for it.
It's a great time to explore your own psyche through a visit to a therapist, or perhaps reading about psychology or astrology.
Talking with a friend about their problems is also instructive, and quite engrossing.
Be principled, know what you want, but continue to indulge his fantasies.