It’s not always that you meet someone who shares a common purpose of life or at least - a similar one. You don't meet people with whom you feel safe and jubilant everyday. You can't build a lifetime relationship on compatibility alone. You need a lot more!!
Being a self-absorbed person, I exactly know how it feels when 'friendly' people barge into your life - desperately trying, inquiring and fidgeting. I do not even know if they believe in building a foundation. And then, there is the second kind of people. They seem to have planned everything before walking down the aisle. They come in, not to change or know us, but to become a part of us; or may be to show that a part exists in you that you didn’t know – till then. They work more with their head and less with their heart; after all, it pays to be as objective as possible. There is never a run out of topics with them. There is never a sour moment. And then one fine day, you recognize that they are your own reflections. The person becomes a mensch when you are seeking comfort; a materialistic when you look for growth; a teacher when you are insecure.
That is when you know you have built a lifetime relationship and that is when you have met your mirror image. I do not know if such relationships are fictional, eroding with time. But I do know there is a sense of belonging which tells me you CAN grow together instead of growing apart.