How to leave your husband?

My life seems perfect, but Im dying inside. I live in a million plus dollar house that is paid for, we own income properties, we both work and have good careers, I am bored out of my mind. Almost every free moment I want to run away....just me and my rottweiler. Other women in my office would be in heaven to have my life, and I just don't want it. I never wanted to be married, but who could say no to such a great guy? SIGH....I have wasted not only my life for the last 13years , but a really great man's life too. I am not the marrying type and I need to go. How can I leave my life without hurting him too much? It's not even for another man, it's just for my need to be alone. Any adivice?