ISTJ + INFP

 These two are nearly opposites (only one preference in common). A mutual desire to grow and mature as individuals is required for this coupling to be successful for the long haul. This isn't a comfortable match, but can be a life-changing one.

Historically, marriage counselors will see opposites marry and divorce and interestingly find the same opposite types to marry again (and sometimes divorce -again). There's always a yearning to "complete" one's self with an opposite type, but it really doesn't work out. If it does work out, it does not do so without a long series of painful reckonings. Intimate relationships need common ground for expression.

Positives of an ISTJ-INFP Relationship:

Shared Introversion: Both ISTJs and INFPs are Introverted types, which means they may prefer quiet, more intimate settings over large social gatherings. They might understand and respect each other's need for alone time.

Complementary Strengths: ISTJs bring practicality and detail-orientation to the relationship, which can help bring the INFP's ideas into reality. On the other hand, INFPs bring a deep emotional and moral focus, which can help the ISTJ consider the emotional implications of their actions.

Common Goals: ISTJs and INFPs often share a common focus on personal improvement and growth, which can bring them together in working towards shared goals.

Challenges of an ISTJ-INFP Relationship:

Different Communication Styles: ISTJs are straightforward and factual, while INFPs are expressive and often communicate through metaphors and symbols. These differences in communication styles may lead to misunderstandings if not managed carefully.

Differing Values: ISTJs tend to value tradition and prefer to work with established methods, while INFPs are driven by their personal values and seek creative, unique solutions. This fundamental difference may lead to conflicts and requires understanding and compromise.

Emotional Needs: INFPs have a deep emotional life and need emotional intimacy, while ISTJs may struggle with expressing emotions and understanding the INFP's emotional needs. This could potentially lead to feelings of frustration or neglect if not addressed.

Understanding each other's personality type can help ISTJ and INFP partners to leverage their strengths and navigate these potential challenges. As always, communication, understanding, and mutual respect are crucial to a successful relationship. It's important to remember that every individual and relationship is unique and influenced by many factors beyond personality type.