How often does real love happen?

I deeply love this guy I dated for several years, but things change and I do not think that he's the one I want to marry. We truly love each other and I wonder if later on we could get back together and work things out (I think that's me being optimistic and missing him). If we stayed together for good I do see a lot of trials and tribulations in our future, but I think we could grow old together. So I want to know how often does real love come around? should I hold on to what we have/had more tightly or just move on? [The general reason I love him but don't want to marry him is that we started dating in high school and as I've grown up some I'm getting a better idea of what I want out of life and out of my life partner...and while I love that guy I just don't know if he's the one for me.]