Why am I so sad for rejecting him?

I was almost married, but something about him reminded me of my former, pardon my French, losers. Still not sure what it was. But I have feelings for him, miss him, want to be there with and for him because I know he would provide for me. And even though I made this decision one week ago and have been seriously depressed by it, a part of me is happy and satisfied. He called it confusion, I call it a revelation because I have ALWAYS hung in there when I should have backed out. I just don't understand the pain, though. If I'm happy for myself for making that decision, then why am I so sad and hurting knowing he'll just move on without me?