Friendship decay works differently based on relationship status so lets break this down quickly. Regular villagers need 10 hearts to stop decay, while potential romantic partners stop at 8 hearts if youre not dating them yet. Once you give someone a bouquet theyll need 10 hearts to prevent decay, and married folks need the full 14 hearts for stability

Watch out for actions that can still drop hearts even at max level, like giving terrible gift, getting caught digging through trash, and even straight up shooting them with a slingshot (or placing cherry, normal, and mega bombs!) married partners are extra sensitive, losing points if you skip daily interactions until you hit that 14-heart mark. Breaking up is rough and drops hearts straight to 5, no matter how close you were before (though you can always erase their memories - ill let you figure that out)

Basically, focus on reaching those key thresholds: 10 hearts for regular folks, 8 for dateable villagers before bouquets, 10 after bouquets, and 14 for spouses. Keep in mind that even when decay stops, being mean can still hurt relationships so maybe dont fire that slingshot at anyone you care about