Staring at the sky, the waves, the trees, the birds and many other things can totally change my mood.
While I was younger, I would go out in the rain. It gave me a level of calmness, but my parents never liked it. I knew they stopped me because of my health, but I always found my way out of the house. It made me happy.
They say the little things make me happy, but Nature isn't little. Nature is everything.