The popular narrative these days is that being in love is the greatest feeling of all. Its concept is heavily exploited in the movie industry, I’d say even in the world of paperbacks. As for being in love, I can only speak about it partially for I was a lover once.
Now, is being in love the most important thing in a relationship? Not really. If it were, trust, loyalty, communication, respect, patience, honesty, commitment etc. would add nothing. Being in love is not enough because it’s just a phase—a mere emotional state. And feelings, as we all know, come and go. Surely, we don’t 'feel' happy all the time—that’s impossible unless you’re on something, but even that wouldn’t last because your body won’t hold up.
In Mere Christianity, Clive Staples Lewis asserts that "being in love is a good thing, but it not the best thing. There are many things below it, but there are also things above it. You cannot make it the basis of a whole life. It is a noble feeling, but it is still a feeling. Now no feeling can be relied on to last in its full intensity, or even to last at all."
But, it does makes us feel good—it reminds us that life isn’t so bad after all. It even inspires us to become a better person, at least for a while. Many would agree that being in love feels far better than being single and alone. Some, like me, only partially agree, because that feeling only comes at the beginning.
Even if we are with the right person, we don't remain 'in love' all the time. That only happens in books or movies. We can’t go on feeling the same way forever. Being in love may be the greatest feeling, but it’s still just a feeling, as Lewis pointed out. Whether we like it or not, it just doesn’t last. There are plenty other things that last: friendships, beliefs, loyalty, knowledge etc.
In fact, even love itself is not enough. You’d need trust, patience, or what have you in order for a relationship to work. Of course, we all know that love isn't just a feeling —love does not equal being in love. Love is more grounded, enduring, relentless and at times unpredictable. In the same book, Lewis writes that love "is a deep unity, maintained by the will and deliberately strengthened by habit." He then proceeded in the context of marriage that both partners "can have this love for each other even at those moments when they do not like each other; as you love yourself even when you do not like yourself"
Thus, it's safe to say that we can love someone without constantly being 'in love' with them. But, if there are any exceptions among you, I commend them. It must have taken tremendous effort to accomplish such a feat.
To wrap up, I'd like to close on this note which I heard somewhere: Love is the whole fireworks show, being in love is the spark that started it.