Here is the honest part first: Leo wants to be adored out loud, and Capricorn shows love by quietly paying the bills and remembering the dentist appointment. Leo plans a big birthday dinner with toasts and a playlist. Capricorn shows up, pays for everyone without mentioning it, and leaves before dessert because there is a 7am gym slot to protect. Leo feels unseen. Capricorn feels unappreciated for the very real gesture that just happened. Neither one is wrong, and that is the trouble.
Both are cardinal, which means both know how to start something and lead it, and neither enjoys being told to sit down. Arguments about whose career takes priority this year, whose parents host the holiday, whose plan for Saturday wins, can turn into quiet standoffs where nobody actually says "I want control" out loud.
But Saturn and the Sun are not enemies here, they are oddly complementary. Saturn gives structure, patience, the long game. The Sun gives warmth, momentum, a reason to keep going. Capricorn builds the container. Leo fills it with life. Leo's confidence pulls Capricorn out of its own head and into a room; Capricorn's steadiness gives Leo something solid to perform against instead of an audience that might wander off.
What actually works is admiration, once it gets spoken instead of assumed. Capricorn respects ambition, and Leo has plenty of it. Leo respects competence, and Capricorn has that too. If Capricorn learns to clap loudly once in a while, and Leo learns that a paid bill is a love letter, this becomes a partnership that builds something real and still enjoys the party afterward.