Aries and Capricorn are both cardinal signs, which means you have two natural leaders trying to steer the same car, and neither one is inclined to hand over the wheel. Cardinal energy starts things. It initiates, decides, moves. So when Aries wants to book flights the moment the idea comes up and Capricorn wants to see a budget and a backup plan first, that is not a personality clash, that is two different styles of leadership colliding in real time. Aries leads with instinct and wants the answer now. Capricorn leads with strategy and wants the answer to hold up in six months. Left unmanaged, this becomes a quiet tug of war over whose plan is the real plan.
But cardinal signs also share a hunger for progress that most pairings do not have, and that is where this relationship finds its footing. Neither of you wants to sit still or rehash the same argument for a week. You both want to fix it and move forward, which means fights tend to be sharp but short. Aries brings the nerve to start the business, ask for the raise, walk into the room. Capricorn brings the discipline to actually build something lasting out of that opening move, the follow-through Aries sometimes skips past.
The friction worth naming is patience. Mars wants results today. Saturn, patient and unhurried by design, is comfortable waiting years for the right outcome, and Aries can read that as coldness or foot-dragging rather than what it actually is. The fix is division of labor, not competition. Let Aries pick the direction and Capricorn build the structure underneath it, and you stop fighting over the wheel and start actually getting somewhere together.