Although INFP is seen as an idealistic flower boy and INTJ has a reputation for being a cold logician, I think these two have much more in common than differences. They can be both distant and private. Both guys sometimes wonder if they are on the wrong planet. Both INTJ and INFP folks are smart and don't tolerate bullshit. Both types are intuitive and have deep thoughts and feelings (although they may not always seem so external). These personality types are also concerned with personal growth and are infinitely curious about just about anything.
INFP values the INTJ's self-discipline and ability to deal with practical matters. His apparent lack of hesitation when decisions need to be made. (Although I know they examine things thoroughly before making decisions, they are not as bogged down with "what if" as we INFPs are.) There are, of course, other types that have these special characteristics, but INTJs can also converse with INFPs on many less practical, theoretical, and even metaphysical levels. INTJ helps INFP take their general ideas and organize them into practical and useful units.
From what I've gathered, INTJs are generally drawn to INFP's strong moral compass, loyalty, honesty, imagination, intelligence, and caring ability. Sometimes they even feel seen by an INFP.
And because these two are introverts, they often enjoy similar activities, giving themselves plenty of space and time.
While INFPs are sensitive to criticism and hate being emotionally excluded, they can also be extremely persistent and resilient.
This disproves INTJ's tendency to fold. Indeed, INFP could view this recall as a worthy challenge. As another respondent pointed out, it seems things generally work out well as long as these two take the time to communicate and are reasonably mature and sensitive to each other.