Hate to be the thorn but it doesn't sound like it was genuine love in the first place.
I'm not saying this definitively, because only you know the answer if you're 100% honest with yourself. However, many people go into relationships for many different reasons, security, comfort, dependency, sex, asset management etc. Most think they're in there for love, but that's because this is what most people want - love. Those that do go into it for love are in the minority, not the majority. You only have to look at the divorce rate. I know here, the divorce rate is at 50%, and 60% of the remaining 50% who are still together...CHEAT! So, when you look at these stats, you can see the cracks surfacing. I'd like to think that more people than my estimate genuinely do go into relationships for love, but love starts with the self and I'm not convinced that most people actually love who they are.
I think this idea that love fades is crap. It only fades because either one, or both haven't put the correct effort that it takes, why? Often because of insecurities and fear. Subconscious demons infiltrate the playing ground. Mental demons kill, and most aren't aware of it.
I was out for dinner last night with a couple of friends. One of my friends has been married to her husband for almost 30 years. He was her soul mate, love at first sight back when she was 21. She is now 49, like me and was saying last night that she loves her husband as much if not more than when she first met him.

Sure, she's had ups and downs, and of course - they fight, but at the end of the day, she can still say firmly that she loves him. There is no one else that could ever take his place.
I have another girlfriend whose husband died almost 2 years ago from cancer. She is another one who married her soul mate. She is now on anti depressants, and drinks every day. She has said that she WILL NOT re-partner because no one can fill his shoes. It was love at first sight for her too.
Me? I've been totally in love with someone for the last 21 years, but he can't come near me, although would like to, but this is a different story, and a complicated one. I've had a few relationships over the years, and I've done nothing other than compare each one to the one that I really want. He was love at first sight too. Unless he turns out to be a raving gambler, cheater or woman beater...I know that he would be the absolute centre of my universe. I just keep falling for him over, and over, and over, and over...even when he goes off at me, and he has many times. I get angry, in fact full of RAGE...but it never removes my feelings of love for him.
I have to say, that from stories I've heard and seen...the only people that actually grow together and whose love grows and matures like wine are those who have experienced love at first sight. If it's not instant, it's not there. I know some will disagree, but the evidence speaks volumes.
I have another friend who was with her partner for 23 years, again...love at first sight, but he left her 23 years later: their business went bankrupt, and he has trouble with intimacy, thus suffering fear. AND because he didn't have enough self love...he allowed his fear to get the better of him. He came back to her, and whilst her anger at him having left clearly won't go until they communicate this...they will not get back together the way it was before. She WILL NOT forgive him for having left her. YET, she can't go more than 2 days without speaking with him. They still go out for dinner etc, but her anger is in the way. My point...here are two people who do love each other but not honestly communicating. She said she always loved him and it just grew and grew.
Maybe you need to ask yourself a couple of simple questions like...
Was she love at first sight?
Was she ever the centre of your universe?
Was she someone you couldn't wait to come home to?
Another good quote I heard, but can't remember who said was...
"You should't find someone with whom you can live, rather - you need to find someone that you can't live without."
Beautiful quote and so true.