Big aims, from opposite ends
Both signs like a large goal, and that’s a stronger link than it may appear. Sagittarius sees the mountain and starts running. Capricorn studies the route and arrives, some time later, with everyone’s gear. Sagittarius gets Capricorn to take a risk and laugh about it, and sometimes to discover that the sky hasn’t fallen. Capricorn teaches Sagittarius that a vision can actually become a business, a book or a house, if you keep turning up.
Faith against proof
Their recurring fight is usually about money and risk. Sagittarius wants to quit the job and sail, or spend the bonus on a trip with friends. To Capricorn, this is frightening and a bit disrespectful of the work they’ve done. Capricorn says, “Show me the numbers,” and Sagittarius hears a door slamming on their whole personality. Then the jokes begin, and Capricorn doesn’t find them funny.
Their manner differs too. Sagittarius says whatever comes up, in public, to anyone. Capricorn cares how the family looks and is mortified at the wedding toast.
A fund for each
A literal, practical fix tends to work well here: one account for the plan, and one for the adventure, with no audit of the second. Sagittarius can bring one finished thing to the table each year, which will mean more to Capricorn than ten promising ideas. Capricorn can agree to one yes per season with no planning at all, and may be surprised at how much they liked it.
Neighboring Suns don’t have a natural angle, so what links you comes from elsewhere. A contact with Saturn like Saturn square Mars can make one person feel braked by the other, and knowing that can take the sting out of it. It isn’t anyone’s flaw.