Trust & friendship
People in Croatia start out with zero trust in one another, but as you get to know one another better, trust grows. Once it does, you're "in" for life. The same is true with friendships (as trust goes hand in hand with friendship, of course). In North America, a stranger can instantly become your best friend, but these "friends" are rarely there for you when you need them the most.
True friendships in Croatia take a very long time to develop (months or even years), but once they do, they'll go above and beyond to support you and the relationship will last a lifetime.