I can definitely write when I’m happy, even if what I’m writing about might not be.
I don’t know why it is that way. My theory is that when we are sad, we feel more like expressing those feelings, to maybe exorcise them somehow. When we’re happy, maybe we’re too busy enjoying the emotions.
I don’t know.
But I write both when I’m happy and sad. There’s not that much of a difference for me, I think.