Think we are expected to come across as being happy all of the time. Society is not really too keen on us expressing the many other emotions we experience.

Yes, you're right there, society seems to have us conditioned to try our best to express happiness above all else, and I am that way myself. Even when I am not in a good place, I will try hard to look outwardly happy and content - I am not sure why that is, but that is how I am.

I love to greet everyone I meet and smile at them, this simple gesture, can change someone's day

I am the exact same! I like to greet everyone, friends and strangers alike. It's a lot more normal in rural areas, you can get raised eyebrows in more urban areas like Dublin, so you kind of have to tone it down a bit in certain places I find.