That thing you are talking about in relationships, where you kind of see yourself through someone else's eyes or you get another perspective from someone on your life and innermost thoughts....well sometimes it comes from the simple novelty of the relationship and doesn't always last. And if it does last, sometimes it gets annoying that someone knows you so well and keeps pointing out ways you can improve or always sees right through you.
You could marry a counselor but you might be like Jerry Seinfeld when he couldn't get a massage from the masseuse he was dating.
Seriously, maybe it's better not to expect that much from a relationship or from any other person outside yourself, really. There is real joy in discovering yourself and that doesn't have to always be shared or affirmed. Have you tried EFT to get at your core issues alone? Seems silly to tap yourself like this but it works.
Iron does sharpen iron though and we all make each other better. I think if you try, you will find that you can have micro versions of this kind of relationship with a lot of other people at the same time. All it requires is some time to talk and enough respect for each other to really listen and take what the other person is saying under serious consideration. This is possible with a sibling, cousin, best friend, parent, even co-worker or fellow smart person on the forums.
If you haven't found anyone that is that interested in hearing you out and helping you grow, you can be the one to start the process by really listening to other's answers when you ask 'How are you, today?' You will be a lot richer if you take the time to develop these type of relationships wherever you can find them.