This is absolutely awesome!

There are some reasons to believe that being happy makes you more productive, rather (just?) than the other way round.

I believe this strongly. Coincidentally, today I was reflecting on my past life-optimization attempts, and seems like the most frequent reason for failure was that at the beginning the idea of the new change made me happy, but after some time I stopped being happy, and then it became difficult to overcome obstacles and I gave up. So I decided that when I try something new in the future, an important task will be to keep myself happy about the project. Even if it means something stupid, like dancing a few minutes before I start the task, or something similar.

Holding a pencil in your teeth could achieve the same thing, just more simply.

(I am not sure what will be the long-term consequences for your teeth. If you keep your mouth partially open for long periods of time, it may change the chemical environment. Maybe try a short pencil or something, so you can keep your mouth closed. And maybe use some pencil-shaped thing without graphite.)