Kindness in Stardew Valley

Kindness is another important theme in Stardew Valley - you're constantly interacting with the residents of Pelican Town and treating them with kindness will lead to them reciprocating. The main way of being kind to them is by giving them gifts they like, and especially on their birthday. This will increase your friendship level with them and creates a positive feedback loop where they're then kinder to you in return which makes you feel more favourable towards them

The higher your friendship level with the villagers, the better the likelihood that they will gift you useful items.
Pam, for example, will gift you battery packs.
Clint can send you copper, iron, and gold bars
Gaining 2 hearts with Caroline unlocks the tea sapling
Linus sends you a recipe for sashimi which is a decent snack
Gus will send you all kinds of recipes in the mail

Plus, being kind - even in a game - makes you feel good! When you perform an act of kindness, it releases endorphins which have mood-boosting effects. This means that being kind can literally make you feel happier!
So go out there and spread some kindness