More of a discussion point here than self-righteous posteuring, but: not ignoring homeless people. Surprised by how many friends or family members will awkwardly look away or say nothing. Takes no effort to politely say no if you don’t have any change or don’t want to give any away.
Breaks my heart a bit because there’s a guy who camps out near where I live who only really draws on the ground and (politely) says hello to people and a lot of people still ignore him even though he’s not even asking for anything
edit: I know this isn’t really an ‘adult’ thing but it is in the sense that adults should know better.