One major comment from my own personal experience as the INTJ in a failed relationship: my first relationship crashed and burned because I was far too arrogant to see just how poorly I was doing at communicating my feelings. I really did care about the girl and went out of my way to be nice and to be thoughtful, all the while assuming that this was the ideal (maybe even the only) way of expressing my feelings. I always asked how her day had gone, I remembered conversations we’d had and followed them up, I said things like “I really enjoy spending time with you,” but I never actually spent the time to figure out how she interpreted my actions. Thus, several months later, I was caught completely off guard when she she had never felt any emotional connection to me, and while we broke up with “no hard feelings” I still regret putting her through that because of my obliviousness.
I say this because I think INTJs are especially susceptible to this sort of trap: we tend to have a core of very intense, very personal emotions that guide every facet of what we think, say, and do, but we lack a well-developed way of expressing those feelings in a lot of the traditional ways: we’re showers more than tellers, but it often never occurs to us that our ways of showing don’t always match what others are expecting. Additionally, we’re highly intuitive, so we’re already used to seeing the truth beneath the surface and it often bothers us when someone states “the obvious” that we’d already observed and deduced. Thus there’s a lot of room for miscommunication (or simply lack of communication) between the INTJ and other types, so establishing a clear channel of communication that both partners are comfortable with is crucial.