Unfortunately, love is rarely unconditional except between mother and child. I have seen it between father and child but while there are exceptions because nothing is absolute, the most common unconditional love is the mother/child bond.
Romantic love almost always diminishes. There are exceptions, but they are few and far between. Most couples stay together for the children and for economic reasons. Except for the latter decades of the 20th century, divorce was rare.. not because they were happy but because it was a commitment they were stuck in. That is no longer the case.
So my point is, WHAT is love? I think the most important love is self-acceptance. Most people struggle with this and despite the fact narcissists appear to be in love with themselves, the truth is they cannot take criticism because they are so insecure. An unhealthy form of self-love sits within self-loathing and lack of self-acceptance.
I see religion as people's need to believe they are loved beyond how they feel about themselves. I mean, it's seductive to be told god loves you so much he will forgive you for anything you have done wrong and he will have paradise waiting for you.
I'm an atheist but I am open-minded about reincarnation. I've come across too many amazing stories to dismiss them. Reincarnation also explains why I have certain people in my life because beyond that, I have no idea why I know them.
The book
"Many Lives, Many Masters" can be life changing. It is worth reading just for the heck of it.