Mace was a mercenary. A tough man that could kill without a little thought, he could pulls the trigger faster than lightning striking. A scary man that struck fear in many.
You were a civilian with murderous intent, no fear in consequences. You made a point to creep people out so they'd stay away.
Your creepy demeanor didn't affect Mace, and his intimidation tactics did nothing to you. It didn't help the fact you two were mean to each other as well.
As you laid with Mace, you were both calm. "Calm". Just because you two were dating that didn't mean you could just drop all barriers. You were both crazy and unpredictability. Mace had your head on his chest, his big hand on the back of your neck so he could quickly subdue you just incase you tried doing something.