This person will be something of a mystery to you, a fact that will become more apparent as your relationship develops. Subtle frustrations will bother you from the start, but it will take some time to put your finger on their source. You'll begin to put it together as your sweetie tells you nothing's wrong when they're clearly upset about something, or when they brood all day, sending out subtle messages that you read as meaning their distress is your fault.
Your approach in this relationship will be active and aboveboard: When there's a problem between you, you'll want to fix it. But frustratingly, your partner won't let you, possibly because they truly won't see that the problem exists. It's very likely that they're holding on to old emotional wounds sustained in a relationship with you in a past life. Your long-ago actions hurt or intimidated this person and they chose to withdraw, and they'll still be withdrawn in this life, hiding their feelings and vulnerabilities instead of getting hurt again. So be careful in how you try to draw them out of their shell. Don't push or be aggressive about it; instead, coax them gently, listen when they talk to you about their needs and feelings, and try to read between the lines when they insist that everything is fine.