Every relationship is special in its own way.
While you may have already moved on from your previous love-affairs to the next, there is always that one thing that leaves an imprint on your soul.
Therefore, it is nothing but natural to make comparisons between the kinds of relationships you have had in the past and the one you have currently.
Not to say that you’ll always find something missing in your relationship. But that does not mean you do not love your partner or are giving up on them.
It is just the good moments that you spent with your ex that tends to kick in and rekindles your memory.