How these two meet
The two of you are extremely good at the first six months of anything.
Nothing has ever been extended past the point where it was still exciting for one of you and still safe for the other.
Cancer makes a place. Sagittarius arrives, fills it completely, is entirely present inside it, and then the horizon does what the horizon does.
The Moon crosses the whole zodiac in 27.3 days and never looks the same on two nights running. Jupiter needs 11.85 years and spends about a year in each sign. One of you changes shape weekly and the other changes address annually, and neither of those is instability, and they cannot be scheduled against each other.
The two who are not here: Cancer’s opposite is Capricorn, who would have built the structure that holds what Cancer feeds, and Sagittarius is what comes just before Capricorn, with the scale and none of the structure. Sagittarius’ opposite is Gemini, who goes and comes back inside a week and is never really gone, and Cancer is what comes just after Gemini, and stays.
So Cancer keeps making a place for somebody who is genuinely in it and genuinely going, and there is no version of this where either of those stops being true.
For Cancer, the work is building one thing that does not require anybody to be in it on Tuesday.
For Sagittarius, the work is naming the return date before leaving, and then returning on it.
The question
Whose version of the week are the two of you living in?
One conscious action
one date, kept
Next time Sagittarius goes anywhere, of any size, a date gets said out loud beforehand and then honoured.
Cancer adjusts nothing around the date. That is the half that matters.
The Moon changes shape every night and Jupiter takes a year to cross a single sign, and no arrangement between you was ever going to bring those into step.
That is not a diagnosis and it is not a warning. It is a timetable, and neither of you has ever looked at it.