In this video legendary screen writer Lawrence Kasdan interviews director JJ Abrams about their work on Star Wars, The Force Awakens.

At 28:10, they talk about the mood JJ Abrams wanted to create for the people working on the movie, and it sounds a lot like happiness at work to me:

When you respect each other, it’s amazing what gets done.
…
It sounds pollyannaish like it’s all, you know, flowers and cookies, but it’s not that at all – it’s a lot of fucking hard work.

Working on movies can be stressful and tough but Abrams realized that a happy set would not just make for a nicer experience for everyone involved, it would also result in a better movie.