There are many different types of love, and even a long lasting marraige goes through the different types at different stages. First, there is infatuation, which includes a strong sense of physical attraction, and those feelings of not wanting to be away from the partner for any length of time. Thoughts ar preoccupied with the beloved. This is what most refer to as "falling in love". Next, there is romantic love. It takes that infatuation to a deeper level.
Then there is the type of love that couples enter into when they are working together to build a home, raise children, etc. At this time, they move out of the first type of love I mentioned, and into a more secure and sharing type of love relationship. This is known as committed love.
When a relationship has endured for a long time, the couple drifts into the companionship form of love, where they enjoy being in other's company, but it is more comfortable and relaxed and accepting. The couple recognizes the faults and sortcomings of the other (unlike infatuation where we are convinced that the person we love is perfect.) They can even admit to not liking each other at times, but are committed to the relationship and feel that they would rather share companionship with this partner than any other, even if it isn't perfect.
The problem arises when we believe that we are always supposed to have head over heels, can't think of anything else, delusions of perfection type of infatuation. This is not the stuff of lasting relationships.