People often think of their words and actions as waves, rolling across the surface, visible but impermanent, ephemeral, inconsequential. But each word you say, each smile you give, each helping hand you extend can fossilize in the memory of someone, to stick with them for the rest of their lives.
Think back to a fond memory you have. It could be a kind comment from a friend, an unexpected word from a stranger, a wisdom received from someone respected. Now ask yourself if anyone else who was there remembers it themselves? Despite the perceived unimportance of these things to those who give them, you remember them, they stick with you, they are a part of your mythology of self.
You are not a soon-vanished ripple, you are not a gentle wind. Pieces of you will remain lodged inside the minds of those you pass by, long after you yourself have forgotten them.