A partner who gets it
Most Sagittarius Suns have been told at some point that they’re too much, too honest, too restless or too hard to pin down. Together, nobody’s pinning. They can leave for a month without a fight, disagree about religion over breakfast and be blunt in a way that would end other relationships. There’s usually a lot of laughing, plenty of friends scattered around the world, and some very large plans.
That sense of being allowed to be yourself is what holds it together. It’s a real strength.
When it stops being fun
Their weak spot is the part of life that isn’t an adventure. Sickness, grief, a dull stretch with a newborn, a parent who needs care. Both may be tempted to reframe the situation with some cheerful philosophy, or to get very busy somewhere else. Each can leave the other alone at just the wrong moment and think they were respecting their freedom.
Bluntness is a hazard too. When two people pride themselves on saying what they think, it’s easy to confuse being honest with being careless. And the bills do still arrive.
Staying put, on purpose
Try making one promise that’s small enough to keep, and keep it. Pick an anchor: a weekly call while traveling, a place you always come back to, one shared account for the boring things. When something’s hard, say “I don’t want to fix this or joke about it, can you just stay here with me?” That’s a harder adventure than any trek, and you might find you’re good at it.
Same Sun signs can look a lot alike from outside and differ greatly within. If one of you has Moon in Cancer or a Saturn contact like Saturn trine Mars, you may already have more staying power than the sign’s reputation suggests.