You cannot be in love with a person; you can only be in love with the projections you put on a person. In this sense, you are in love with your own idea.
Inevitably, your idea will change. Have a look at this graph examining a new relationship, from Jonathan Haidt’s The Happiness Hypothesis:
Note the two kinds of love–passionate and companionate–and note the danger points. These danger points are a trap: they are the moments we convince ourselves we’ve found “true love”, and in our grasping for it we inevitably lose it. In our loss of it we convince ourselves we picked the wrong person.
All the while, companionate love was building. Have a look at the next graph, examining a 60-year relationship:
One love is not better than another, but it’s worth remembering that passionate love and companionate love are distinct: one does not lead to the other, but follow separate time courses.