As you've probably already experienced, you two have a hard time with each other when it comes to growing as individuals within the relationship. Your partner is on a highly emotional path toward self-knowledge throughout your relationship; they're doing a lot of hard work and personal transformation, and this personal struggle invariably ends up pulling you in, even when you don't want to be. A further part of the problem is that you have such different ways of meeting issues and translating perceptions -- you're polarized between the mental (you) and the emotion (them), and you have a hard time even speaking the same language, much less understanding where the other is coming from.
A third part of the problem is your partner's tendency to project their subconscious need for change onto you. While this should be a personal process, one that would go on whether they were romantically involved with you or not, instead, they try to change themselves through you somehow. They might focus overmuch on the relationship, ferreting out where your connection needs change, and put too much energy into that and not enough into themselves. It could be that the relationship is just fine, after all -- and it's them, or you, that needs the work! You two might have a hard time getting along as a result, especially if you start putting each other on the spot about your beliefs and trying to force a defense of the qualities that make you who you are.