Just now, I was practicing Spanish on Memrise. I used to speak each word aloud while writing it, but I had stopped doing that over the summer to not annoy other people in my hostels. So imagine my surprise when I started doing it again and my mood completely changed within a minute - from kind of meh and relaxed to full of energy and happiness.
Why full of energy? I tend to move through words pretty fast, thus speaking at that speed is quite energetic and fast too. This looks like a promising approach to alter my own mood, to raise my average and median happiness level in the long term.