The best marriages just don’t happen because a couple fell in love once. Great marriages happen because two people fall in love over and over again with each other.
Personally, I have fallen in love with my wife on a number of occasions. I remember falling in love with her when we started dating. Then I fell in love with her again when we got married and realized how she made me better (not just by nagging). I fell in love with her again after she became a mother and I saw how being a mother was her passion.
As you are married longer, look to fall in love with your spouse again. It keeps things fresh and makes for a great marriage.