A public garden depends on visitors leaving something beautiful for the next arrival.

Public places are held together by people who gain nothing from it. Nobody profits personally by leaving the bench clean, carrying litter home or not picking the flowers, and the pleasure of the whole place depends on almost everyone doing so anyway. It runs as a chain of small deposits made for strangers. One person taking what they like is enough to start it unravelling.

Leave a public space slightly better than you found it, even by a single piece of litter. Picture the next arrival as somebody particular rather than as nobody at all.