Melting the Ice with Billionaire's Touch

I have everything in my life all figured out. My job in a Manhattan empire is perfect, allowing me to maintain a quiet and organized existence. After a childhood filled with painful memories, abuse, and a useless mother, this sense of security is a necessity for me. But along with it comes a problem that could disrupt everything I thought I needed.
My promotion places me in close proximity to Jacob Carrero, a young, incredibly attractive, and playboy billionaire with a notorious reputation. I now find myself stuck as his right-hand man, spending every waking moment with him. It doesn't take long for me to realize that he's exactly the type of person who could drive me crazy, and not in a good way. We're like chalk and cheese. He's impulsive, confident, laid-back, dominant, and enjoys casual sex and dating without much thought. I, on the other hand, am compulsive, reserved, and cautious.
Despite his carefree attitude, Jacob is the only one who can break through my composed exterior. He's not phased by my closed-off demeanor and cool manners. But as much as I may want to, letting him into my heart is another thing entirely. My painful past has made me wary of men, and I have no desire to let anyone get close enough to hurt me again.
However, Jacob Carrero is not someone who takes no for an answer. He wants to be more than just another person seeing my façade, who is learning how to break through my defenses.
What should I do?