I think it is that and a bit about not letting envy of other people’s wealth/property interfere with your ability to be happy, eg: keeping up with the Jones’s. Obviously you can be wealthy and still not be happy (see Kurt Cobain, Robin Williams, etc) but for the vast majority I think the thing is that money, or specifically the lack of it, is the source of a quite a lot of unhappiness. Now, maybe if I had a million dollars, I’d still be a miserable bastard, but given that most of the problems I have now are either directly money related or significantly impacted by the lack of said money, I kind of doubt it.