You touch on something here that's interesting, but I think it's more than that. This little nugget of a poem holds so much truth, but it's also unexplored, too, I feel. I don't think that happiness gets in the way of poetry, I think poetry is about the juxtaposition between happiness and sadness, and all those "contradicting" emotions coming together like a fault, creating tension and making a poem. Or an earthquake. A breakdown. I fucking hate drama, and I don't even think it's ABOUT the drama, but how we handle it. Some people are completely unphased by big things, like life-changing events, but the small things force them to write a poem. I don't know if I've ever written a poem about happiness, not that I can recall, but I've never written one out of anger either. I don't really think it's even about once emotion, like emotion, or sadness, but the exploration of many together. I don't know, now I'm rambling. I don't know if happiness gets in the way of poetry. In fact I think one of my biggest highs is finishing a poem. Few things make me happier than that.
Some people need to create drama if enough is not provided in their lives. It's all part of a well balanced diet, I suppose. What I really pity are those who know not poetry or artistry at all, treating it like some foreign esoteric.