Bummer. Was hoping you had an explanation. Christian explanations are boring and cliche: because I believe the Bible is true, because I met Jesus, because I just know. Non-believers usually have far more interesting explanations.
I was thinking about this last night, and think I may have some explaination at least for where I got some of the ideas about the afterlife that I have.
First, I am a bit of a romantic, and I do think that most people search for someone here on earth to be with (although it may take a while to get to the point where they are conducting this particular search). I couldn't imagine being in an afterlife without someone to share it with, just like I want to share my life here on earth with someone. I also believe that most people are capable of falling in love with more than one person but that it is quite possible that none of those are really their true soul mate. I have known a least a few people who have felt deep love and devotion to more than one person in their lifetime, and I believe that this is natural (although I think that it also has a little to do with the maturation of a soul as to whether a person can do this or not). I'm not sure exactly how I derived this particular view, but I know that it isn't uncommon to find people that believe in soulmates, just those that have a more optimistic viewpoint on finding a soulmate.
I think my views about a soul maturing over many lifetimes comes from views on the maturation of societies, my own and some other people that I have known, at least partly. I had a teacher once point out to my class that societies, and even humanity as a whole, seems to mature with time. It is like you can almost observe the different stages of life in societies as a whole, at least it seems that way to me. Now, not every society matures, as a whole, as quickly as some others might mature.
And I know that no matter how much a try, I cannot access most of my memories but that they did influence who I am. I guess this is why I can see a soul working somewhat the same way, only on a longer timeline.
I think some of my ideas came from just looking into the different religions and cultural beliefs in general, and finding the similarities. And, generally, I am a pretty positive person, so I know that I am more likely to question any negative rule/custom/belief from a culture or religion than I am a positive rule/custom/belief.
My family can take some of the credit for me believing that a higher power would not be likely to make up arbitrary and unfair rules because growing up I was taught to question such things (although, I was taught to do so as politely as possible). Along with this, I was also taught that God was fair and loving and that He gave humans free will. This is one of the reasons that I question any religion that has rules for getting into or a better afterlife, especially when such rules are in some way unfair to people or a certain group of people, because these things do not logically fit with a fair and loving God that gave us free will.
Now, I can say that I think some of my beliefs were influenced by media, including books, TV, and movies. And there is definitely influence from individual beliefs of my family as well, and even some of my friends and acquaintances.