Gallup has started tracking American's self-reported well-being on a monthly basis. As shown in this graph, American had a good month in February. The trend only covers the last two years, so it's hard to speak of historical changes. However, I was struck by how few Americans report themselves as suffering. Most of us are thriving or struggling.
At a different site, Gallup presents measures of a wide range of indexes, and the overriding theme seems to be one of seasonal effects. We're less happy and healthy during Winter.... who would have thought!