If unnecessary guilt comes under the heading of unhappy I would say atheists are happier in that regard. That said, delusion can make a person unjustifiably happy. I think atheists are largely people who can be happy or sad and do so without the aid of imaginary reasons. A few on here have given me a subtle hard time for saying meditation helps keep my emotions in check, one guy offered to have me babysit, (thanks I have 3 of my own) but simply if you have the tools and make an effort to be accepting of how things are you can lesson the swing of emotions a bit, you never stop being human, it’s truly just a tool and not a panacea. Now I have also found atheists on here treating nonbelief as a religion, they seem still to struggle with accepting reality and are looking for a replacement to religion, they may find happiness more elusive. I prefer not to call the religious morons, I prefer misguided, once you insult someone they are gonna dig their heals in and the chance of them changing is I’m sure greatly diminished.