I have had much similar experiences. As an experiment I started smiling to everybody walking past me on my way to school. Every day and mostly the same people. At first some looked at me weirdly, but little by little people started smiling back. This evolve even further. First to a smile and a nod, then a smile and a good morning and finally a big wide smile and
‘’Good morning, have a nice day’’. It’s amazing what such a little thing as smiling can do.