It's tragic to think that the ones we love and cherish the most usually are the fastest to break our hearts and/or abandon us. My ex said the same thing to me when we first started dating... the thoughts of love, marriage, and kids were just a fantasy in his head during the honeymoon stage, once that phase ends, they start to change either for better or for worse.
The pain that comes after a breakup is indescribable and I can sympathize with your feelings of rejection. Love is a temporary feeling unfortunately and we can't take what others say at face value because people aren't reliable. They can go from being the most important person in your life to suddenly disappearing one day. But the good thing is, she's not the only girl out there who exists, it will definitely hurt the remaining days to come for sure, since she was special to you, but five months from now, you'll begin to think less due to time. I still have bad days myself after the breakup, but it wasn't as difficult as the beginning. My recommendation is to vent or write as much as you can about it until you reach a point where you're ready to move on.