It seems to me that many people do not really understand the idea of love. I wrote a book with that as the title, 'Understanding the Idea of Love'. You can find it here theotherdavidallen.com

Many people think that the emotions associated with love are love itself.

Essentially, love means to value something very highly.

I value the people I love very highly.

Those I do not value highly, I do not love. It really is that simple.

Also, in order to love someone, I must respect them since respect is essential to valuing something.

I love reading, writing and intelligent conversation. That is because I value those three things very highly.

If you no longer believe that you love something or someone, it is because you no longer value them highly. And, in the case of people, probably you have lost respect for them as well.