How do you walk away without really saying goodbye?

 How can a man who says they love you just say it's over without a real explanation?  That's the question that's been on my mind day after day night after night.  The only thing I can come up with is that he really didn't love me. But why would he have stayed with me for 12 years.  Was it society telling him one thing and his heart telling him another?  Why wasn't he strong enough to say the hell with society, I made my own decisions, deal with it?