Lost Connection
When you’ve been with someone for a long time, you have to accept that your feelings for them will change as time goes by. Sometimes, this means that you will form a deeper connection and at other times, it means that you will drift further apart.
The OP and her ex-fiance were high school sweethearts who had been together for over 10 years. While it sounds picture-perfect, the OP started to realize that she just wasn’t feeling connected to him anymore and had to break things off six months before the wedding date. We suppose it is what it is and there’s not much anyone can do about it.