You can see why people got angry in 2008: they had thought things were particularly good. In fact, perceptions in 2006 and 2007 were better than at any time since. And it turned out there was a nasty shock in store. It was the shock that annoyed people, I suspect.
Then note that people think that things have been improving progressively since 2011. In that one trend is the explanation for the election result in 2015.
People think they’re better off, and that’s the biggest risk George Osborne faces