When you give feedback to your favorite podcast and they make a small adjustment for the better.
When you share your work with someone who points out that it sounds a lot like an author they've heard of, and one who inspired your work.
When your almost three-year-old puts his dirty dish in the sink.
All small. But all big.
Small because they aren't ground breaking things. But big because combined together they all show you that you're making a difference, you're on the right track. And that's how things change - a bunch of little things, over time, adding up to a big change.